In 2016 I bought a Cessna 182. Before that, I was renting Cessna 172’s, and there was a moment when it became clear to me that it was time to stop renting and start owning.
It can really be boiled down to a 3-part decision… Freedom, Frequency, and Finances. Deciding whether to buy or rent can be a complicated decision, but for me, boiling it down to these 3 categories made it way more clear.
Note: This post was adapted from the original video posted on this topic here:
Freedom
The first category is freedom. Freedom just means do I have the freedom I’m looking for in aviation.
In some rental and club situations, it might be challenging to take the airplane for a full weekend or overnight trip. Whereas in ownership, you end up having all of the freedom you could want because you own the thing and can fly it when and where you want.
Now, some rental and club scenarios have great access to airplanes and freedom isn’t an issue. If that’s your situation, that’s awesome. That’s probably worth staying in.
I was renting by the hour and I had very little freedom… The main time the airplane was available was during the evening on weekdays which is not convenient at all.
I watched a lot of sunsets in the plane but that was about it.
So, the questions to ask are:
Do I have the amount of flying freedom I would like in a renting situation? Or am I maxed out and the only way to unlock more freedom is by owning the airplane?
For me, I wanted longer rental blocks (weekend trips) and spontaneity. So the verdict on freedom eventually was OWN.
In regards to freedom, it’s worth noting that renting could also mean joining an ownership club, too. Ownership clubs can sometimes be a good blend of having good access to the airplane while also spreading out the costs among many owners.
But since you don’t have total ownership or unrestricted unlimited access to the airplane I’m going to reference clubs in the same boat as renting for the purpose of this discussion.
Frequency
Second is frequency. How often are you able to fly? Does your rental situation allow you to have the spontaneity you want?
If you’re in a rental situation where you’re flying about as frequently as you want or need, renting can be a great thing.
When I rented I had to think pretty far ahead. I wasn’t really able to say “the weather looks great tomorrow, let’s go flying” much, if ever.
When you own, frequency gets solved because you have unlimited access to the aircraft. You don’t have to think ahead and reserve the airplane before someone else.
I like having control over my schedule, and so just having control over the availability of my airplane is a really great thing.
So, the questions to ask are: Am I able to fly as much as I realistically want in renting? For the most part, am I able to fly when I want?
When I was renting, I was renting like 3-6 hours per month but I wanted to fly 10 or more per month. So for me, eventually the verdict on frequency was OWN.
Finances
Next is finances. Usually the first two, freedom and frequency, favor owning versus renting. It’s the finances that are the sticking point. It’s expensive to fly.
Finances can be tricky because you can’t just look at the hourly rate of owning vs. buying… you also have to look at the total amount spent for the year.
Let me explain.
First is comparing the hourly rate… when you’re renting, the hourly rate usually stays the same whether you fly a little or a lot. Sometimes you can get discounts for buying bulk hours but let’s ignore that for the time being.
The challenge with the hourly rate is that you get a bill on your credit card after every flight and it’s hard not to say “was that sunset worth $500”. (show on a chart a flat line). So you might want to own to bring your hourly rate down…
When you own, you have fixed costs that you have to pay for regardless of how much you fly: Insurance, hangar, annual inspection, etc. and you have variable costs like fuel that you only pay when the engine is running.
If you fly a little that year, your hourly rate is higher than if you flew a lot, because you don’t have as many hours to spread those fixed costs across. The more you fly, the lower your effective hourly costs.
If your hourly costs of owning are the same or less than renting, then that’s a pretty clear winner.
If your effective hourly costs of owning are still higher than renting at your projected number of flight hours per year, then you just need to decide if that premium is worth it to you to get all of the freedom and frequency you could want.
So, that’s one way to look at the finances. The second is comparing the total dollars you spent in a year.
In renting, your money spent varies directly with the number of hours flown.
When you own, you have fixed costs like your hangar, insurance, annual inspection, etc. that you incur even if the airplane doesn’t fly at all that year. But your variable costs like fuel are probably a lot less than the cost of renting.
So what happens is eventually your costs will intersect at a certain number of hours flown and money spent.
That makes it easy to show when it’s the same or cheaper to own, but the question to ask here is this: is it realistic to spend that much in the first place to achieve that break even?
In other words, if that breakeven happens at $20k spent per year but you planned on spending $10k per year, then you’d still want to rent. Even though it’s more expensive on an hourly basis, your total amount spent is more within your budget.
So, the questions to ask here are: Would owning be similar in price (or even less) versus renting? Or is the extra expense worth it for the freedom and frequency? Or based on how much I fly, is owning prohibitively expensive versus renting?
For me, while I didn’t love the hourly cost of renting the airplane, I couldn’t yet afford the annual commitment of owning one just yet. So I rented for a while until I could afford owning it. And that brings up an important point here…
It’s going to be different for everyone.
If you take two people evaluating the same rent vs. buy math, but their own personal financial circumstances are night and day different, they might come to different conclusions. So financially I can’t definitively say when you should own vs. rent.
However, here is my rationale on the finances of aviation. You should come up with yours, but here’s mine in case it helps. It’s simple and comes down to only two rules.
My Rules for the Finances of Aviation
Rule #1: Live within your means. Spend less than you make. That way if you make a little or make a lot, you’ll never be upside down financially.
Rule #2: Intentionally decide where you surplus time, energy, effort, and resources will be dedicated, based on what’s important in your life. Come up with a plan on how you’ll spend your time and money, and why.
Everyone is going to have a different take on #2.
For some people, they won’t get guac at chipotle because it’s extra and they do the math to know what that $1.95 would be worth if they invested it today and waited 50 years.
For me, I’d rather eat the guac.
I still want to save and invest and such but people will have different goals and priorities.
I don’t spend all of my money or time on aviation but there’s a balance there. You should find what your balance and priorities are.
And if you can fit aviation into it and also not break rule #1, then I think you’ve got a green light.
So ask yourselves the questions we just covered about freedom, frequency, and finances. If and when all three lights blink green, there’s a solid argument for owning.
Check out our free Airplane Buying Roadmap that provides step-by-step instructions about how to buying your first plane:
Why Are Some Propeller Blades Curved? (Scimitar-Shaped)
Just a few years ago, if you looked around the typical general aviation ramp, you typically didn’t see much diversity in propeller design. However, that has been changing. Curved propellor blades are starting to be much more common.
Why are some propeller blades curved?
Propeller blades serve the same purpose as swept-back wings, which is to reduce drag at the tip of the airfoil where the blade speed is the highest. This increases the efficiency of the propeller when the tip reaches high, subsonic speeds.
A propeller’s main job is to convert the rotational force of the engine into thrust. Small gains in propeller efficiency make a big difference.
An efficient propeller converts more “lift” generated by the blades into thrust than an inefficient propeller. One of the design elements that improves efficiency is having a curved propeller blade.
In order to understand why curved propellers are more efficient, it will help to first take a moment and think about a special type of airfoil – swept wings.
When planes got significantly faster at the dawn of the jet age, there were two phenomena that made further speed increases difficult to achieve, and swept wings (angled towards the rear of the aircraft) helped overcome these problems.
The wings of this Boeing 747 – and nearly all other modern jet airliners – are “swept” back in a V shape. Image Credit.
The first phenomenon has to do with drag – aerodynamic drag increases as the square of velocity. This means that a doubling of speed results in a fourfold increase in drag.
Aircraft designers realized how valuable it would be if they could find a way to “trick” the airfoil into thinking that its speed was less than it actually is – even by a little bit.
Another phenomenon dramatically increases drag at high airfoil speeds. Namely, the shock wave that develops around airfoils when they approach the speed of sound (around 750mph at sea level) adds a large amount of drag.
This is known as wave drag.
The wave drag created by the formation of that shock wave is substantial. In fact, it is so substantial that it gave rise to the term “sound barrier”.
Chuck Yeager broke the sound barrier in a rocket-powered Bell X-1 on October 14th, 1947 Image Credit.
Aeronautical engineers contended with these two phenomena – the square relationship of velocity to drag, and wave drag (shock wave induced drag).
As the fastest aircraft of the day approached speeds near the speed of sound, reducing drag was paramount to getting the most efficiency out of aircraft wings.
An ingenious solution was devised in Germany in the 1930s: the swept wing.
The swept-wing plan form features a leading edge that is angled to the relative wind – giving modern aircraft V-shaped wings.
The airflow over swept wings can be thought of as being divided into two components; the spanwise airflow and the airspeed sensed by the wing.
As is illustrated below, a swept wing moving through the air at Mach 0.85 displays drag characteristics as though it is only going Mach 0.70 thanks to the sweep.
The aerodynamic drag decreased dramatically thanks to the square-law discussed before. Even better, the airfoil is not generating wave drag associated with near-supersonic travel.
The result is significantly less drag over all – suddenly, much higher speeds at lower fuel burns were possible.
“OK”, you say, “I understand the idea behind the swept back wing, but my Cessna 172 doesn’t travel anywhere near supersonic speeds. So, how does this apply to me?”
When the propeller in my plane is spinning at 2,500 RPM, thetips of the blades are moving at 558 MPH. That works out to Mach 0.74!
You can compute your aircraft’s propeller speeds by using this propeller tip speed calculator found at Warp Drive Props.
Several aircraft have propellers that are large enough and spin fast enough that the tips move through the air at transonic speeds (between Mach .80 and Mach 1.2). Once the airfoil is transonic, the sound barrier shock wave-induced drag becomes a hugely important factor.
Even if your propeller tip does not travel at supersonic speed, finding a way to sweep it back will also reduce the aerodynamic drag.
Since that drag has a squared relationship with blade speed, any reduction at those high speeds makes a big difference on drag.
In this diagram, the green arrow shows the wind a “normal” propeller would experience. By curving the propeller, we can separate the wind into spanwise flow (red) and the flow the airfoil experiences (pink), which is perpendicular to the curved blade. Because the pink arrow is shorter than the green arrow, the propeller experiences less drag overall.
The Curved Propeller is a “Swept Back” Airfoil Planeform
The best way to enjoy the benefits of a swept airfoil on your propeller is to curve the blades.
The curve, as opposed to a straight-line sweepback like found on an airliner wing, is desirable because of the speed difference between the root and tip of the propeller.
The blade root is moving relatively slowly (around 145mph in a Cessna 172 at 2,500rpm) compared to the tip. So, there’s no need to sweep back much more than the tip in most general aviation propellers.
For propellers that are swept back, the most pronounced curve is at the tip where the airfoil speed is the greatest (see image above).
The curve of the blade resembles the look of a scimitar. Hartzell even makes a propeller called the “scimitar propeller” for this reason.
Is there a significant performance gain with a scimitar-type propeller?
Unless you have an aircraft whereby the tips approach or exceed the speed of sound (like a Cessna 185, with its giant 86” propeller), the performance gains from a curved propeller may be negligible in most general aviation aircraft.
Others claim that they see noticeable performance gains even in aircraft that don’t produce that type of tip speed. You should talk to a reputable propeller shop if you have more questions about your personal aircraft.
Here’s how that Cessna 185 with a large prop sounds, by the way. Sound on!
When were curved propellers invented?
Interestingly, wright-brothers.org notes that the famous Wright brothers developed “bent-end” propellers as early as 1905.
The Wright brothers focused a tremendous amount of research on propeller design and were ultimately able to achieve propeller efficiency numbers of 78%, compared with modern-day propellers which are around 83% efficient.
However, the earliest successful curved propeller designs are largely credited to Lucien Chauvière. His “Integrale” propeller design was commercially successful and featured a scimitar shape.
Are there any other benefits to a curved propeller?
Other than the aerodynamic advantages resulting in a gain in propeller efficiency, there are a few other advantages worth mentioning.
In aircraft with propeller tip speeds that generate a shock wave, an important benefit of shock wave reduction is a quieter propeller. The shock wave is what can produce little sonic-booms as the propeller spins and the tips go supersonic.
The curve may bring that effective speed down to a subsonic level, making for a much quieter aircraft in the cabin and on the ground. Quieter propeller airplanes are much more popular with the flying public and residents nearby airports.
The other, more subjective, benefit is purely cosmetic. The scimitar-style blade just plain looks better to many.
When the time comes to replace your propeller, that may be a good-enough reason to take the plunge!
Take a close look along the length of a propeller, from the tip towards the spinner, and you will likely notice that it looks like the propeller twists. This twist along each propeller blade is, of course, very intentional and necessary to extract the most performance out of the propeller.
Why are propeller blades twisted?
Propeller blades are twisted because the blade tips travel faster than the center of the propeller. The twist of the blades compensates for this speed difference so as to produce uniform thrust along the length of the propeller blade.
A propeller’s main job is to convert the torque produced by the engine into a linear force that propels (hence, “propeller”) the aircraft forward.
Thrust is developed because as the propeller moves through the air, it produces a force – just like a wing. The main difference is that while the wing is oriented to produce lift (upwards force) meant to counteract weight (downward force), the propeller is oriented to produce thrust (forward force) to counteract drag (rearward force).
The Propeller is an Airfoil
Thrust is produced by propeller blades because each blade is an airfoil, just like a wing. Stand back for a moment while on the ramp, and you’ll easily see that each blade of a propeller has a shape similar to a wing, along the entire length of the blade from the hub to the tip.
The “bottom” of the blade (toward the cockpit) is relatively flat and the “top” of the blade (facing forward) is rounded just like the more familiar wing-type airfoil.
The leading edge of the propeller is rounded and the trailing edge is a bit more pointed. Again, this is just like what is found in most airfoil designs.
As air moves over and around the blade, explanations provided by Bernoulli and Newton provide insight as to how thrust is created.
Bernoulli taught us that an area of low pressure develops in front of the propeller blade (over the “top” surface). The higher air pressure behind (“under” the blade) wants to fill the low pressure void and “pushes” along the length of the blade, pushing the entire airplane forward.
Newton also explains some of the thrust by pointing out that as the propeller moves vast quantities of air backwards along the longitudinal axis of the aircraft, the “equal and opposite” reaction is the resulting thrust.
The production of lift by an airfoil is a complex topic that is better explained in an aerospace engineering course, but the explanations above are correct enough for our understanding as pilots.
However, a propeller blade is subject to an interesting phenomena that is unique to the rotational movement not present with a traditional wing: the airfoil is not traveling at the same speed along its entire length.
Propeller RPM vs. Blade Tip Speed
The relationship between propeller RPM and the actual speed at which the airfoil moves through the air is a very simple yet dramatic concept that you may not have thought much about.
A typical Cessna 172 propeller has a diameter of 75”. The circumference that the tip of the propellers travels through each rotation is therefore 236”.
When that propeller is spinning at 2,500 RPM, the tip (37.5” from the center of the hub) has to travel almost 20’ in the same amount of time that the inboard part of the propeller (10” from the center of the hub) has to travel 5’.
In other words, on a Cessna 172, at 2,500 RPM, the tip is covering almost 4x the distance that the inboard part of the blade is on each revolution.
This creates a pretty substantial speed difference between the tip and the root. How much of a difference?
Warp Drive Props has a really cool propeller tip speed calculator that can be used to calculate that difference. Check it out!
On a 20 degree Celsius day and at 2,500 RPM, thatCessna 172 propeller blade tip is traveling at a speed of 558 MPH (that’s Mach 0.72 – and you thought everything about a Skyhawk was slow!).
10” out from the hub, at the root of the propeller, the propeller is traveling at only 149 MPH. That’s a 409 MPH difference!
Propeller twist compensates for the speed difference along blades
With that huge difference in speed between the root and the tip of the propeller, it makes sense that if the desire is for the blade to produce lift evenly along the entire length of the propeller, blade twist is needed so that the “wing” traveling at 149 MPH is producing the same lift as one traveling at 558 MPH.
The only way to accomplish that is to set the angle of incidence of the blade so that the angle of attack at 149 MPH is higher than it is at 558 MPH.
Image Credit: Pilot’s Handbook of Aeronautical Knowledge, Chapter 7
This is why, as you look down the length of the propeller blade, you will notice that the root of the blade is angled to take a much larger “bite” of air than the tip is. This allows a more equal distribution of lift allowing the entire length of the propeller blade to be a producer of thrust.
The center part of a propeller blade travels more slowly, with a high angle of incidence. The outer part of a propeller blade travels much more quickly, with a lower angle of incidence. Early airplane designers used trial and error, wind tunnels, and flight testing to achieve this.
Engineers these days make use of advanced computer modeling to design an optimal propeller blade that balances the demands of thrust, efficiency, weight, strength, and cost.
Believe it or not, wings and propeller blades share this design feature. Most airplane wings are designed with some twist, called washout. There is a higher angle of attack at the base of the wing compared to the tip of the wing.
We’ll link a longer article about washout here when it’s completed, but the basic design idea behind washout is to ensure that the tip of the wing is the last part to stall – this is important to guarantee aileron authority near a stall condition.
What about curved (scimitar-shaped) propellers?
Some propeller blades have a slight curve towards the tip, in the shape of a scimitar. There are good reasons for this kind of design that are outside of the scope of this article but are very interesting nonetheless.
It was actually our very own Wright brothers who first made successful use of a twist along the length of a propeller blade. They had done some wind tunnel testing for their wing design and recognized the importance and relationship between angle of attack and the production of lift.
The 1903 Wright Flyer was the first successful airplane design. It made use of two spruce propellers with a diameter of an impressive 8 feet each.
In this colorized photo, you can see the Wright Flyer had twisted propeller blades just like modern designs. Image Credit.
In this article, the authors point out (using some very sophisticated formulas) that the 1903 propeller used by the Wright brothers achieved about 82% efficiency in producing thrust and that their propellers match, almost exactly, modern day propeller design across the outer 2/3rds of the propeller length.
They point out that modern high performance propellers are around 90% efficient while a typical Cessna 172 propeller is around 74% efficient at cruise speed.
The Ingenuity Helicopter, which was the first aircraft to fly on Mars, shares some basic propeller design elements with the Wright Flyer from 118 years before. Image Credit.
Further Reading: Propeller Topics
Here at Airplane Academy, we love propellers and have written extensively about them. Here are some of our favorite articles about propellers.
Walk the flight line at any GA airport and you will likely see a mix between 2-bladed and 3-bladed propellers. Some more expensive, high-performance planes may have 4 or more propeller blades.
Besides arguably looking better, there are performance differences to be considered when comparing the blade count of propellers.
What is the difference between 2, 3, and 4-bladed propellers?
Two-bladed propellers are typically used on smaller engines (under 300 horsepower) and are lighter and more efficient. Three-bladed propellers are quieter, have better ground clearance, and create more power but also more drag, and are used on larger engines with enough torque to drive the propeller.
In this article we will discuss these differences, their causes, and what considerations you should make when deciding on what sort of propeller will fit your needs.
How Propellers Generate Thrust
First, let’s discuss how propellers generate thrust in the first place – then we’ll get into the differences in propellers with varying blade counts.
A propeller’s function is to translate the power generated by the engine into useful thrust. Thrust is generated by a propeller in a very similar way as wings generate lift.
Propeller blades and wings are both examples of airfoils. It is helpful to keep this in mind when considering the advantages and disadvantages of 2, 3, or 4-bladed propellers.
As the engine turns, it spins the propeller. As we all learned in primary flight training, an airfoil generates a force when moving through air. A propeller blade generating thrust is analogous to a wing generating lift.
More thrust is a great thing – it helps with take-off, climb, and cruise performance. But much like decisions made when designing a wing, engineers have to make design decisions when deciding what propeller to fit on a plane.
The 2-Bladed Propeller
The efficiency of a propeller describes how much of the engine’s power is directly translated into useful thrust. A higher efficiency means that more thrust is produced with a given horsepower.
Thrust is analogous to lift, and remember- as more lift is generated, drag increases as well, reducing efficiency.
As we increase the number of blades, thrust increases but that means more drag and less efficiency.
Our relatively low-powered general aviation engines don’t have much excess horsepower which is why we typically see 2 blades mounted on our engines. 2-bladed propellers are the most efficient at translating horsepower into thrust.
So, why not just increase the thrust created by a 2-bladed propeller by increasing the length of each blade? It sounds great – you could enjoy the efficiency of 2 blades and get the thrust you want by just increasing the blade length.
It’s a good idea, but there are two primary reasons why you can’t just increase blade length ad infinitum.
First, landing gear can only be so tall and clearance between the propeller and the ground has to be assured.
As the blades get longer, the tips get closer to the ground. At some point when increasing propeller blade length you will run into clearance issues.
My Beechcraft Sierra, for example, has a pretty tall set of landing gear for its size of plane. It has a 76” propeller diameter. In comparison, a Piper Arrow sits closer to the ground and has a 74” propeller.
A Beechcraft A23 with tall landing gear, a long 2-bladed propeller, and a spacious cabin. Image Source.
The two aircraft use the same IO-360 engine, both producing 200 horsepower. The Beechcraft Sierra has a much larger (and therefore drag-producing) cabin, but both planes have similar real-world cruise speeds. This is partially due greater thrust produced by the longer propeller on the Beechcraft.
The other limiting factor on propeller length is that the longer the blade is, the faster the tip is spinning.
You may recall that the propeller blade is slightly twisted so that the blade near the hub is at a much greater angle of attack than the tip of the blade. This helps to distribute lift evenly since the blade nearer the hub is spinning at a slower speed than the tip.
As propeller blade tips get close to supersonic speeds, drag increases tremendouslyand takes a toll on the amount of thrust being generated. Engineers have discovered that it is disadvantageous to allow the tip of the propeller to go supersonic.
Using the Beechcraft Sierra as an example, at 2,700 RPM and 10 degrees Celsius, the tip is traveling at 0.81 Mach, or over 600 miles per hour!
I didn’t think anything on the Sierra was capable of speeds like that!
Because of the lower power ratings of small general aviation planes, you will typically find 2-bladed propellers on the majority of planes at your local airport. There are many situations however where installing 3 or more blades makes more sense.
3 Blade Propellers – Pluses and Minuses
Many aircraft either come with, or have STCs for, 3-bladed propellers. While they may not be as efficient as 2-bladed propellers, there are some advantages of having that third blade.
Designing an airplane is all about making tradeoffs.
Engineers choosing a propeller to fit to an airplane have to decide the right balance between engine torque, blade efficiency (blade tip speed which is a function of engine RPMs and blade length), ground clearance, and noise, to decide the optimal scenario.
Pairing a powerful engine with a two-bladed propeller doesn’t mean you can just spin the blades faster, due to the reasons stated in the previous section. This can mean leaving a lot of torque on the table unless you add more blades to the propeller.
Thefirst advantage of a 3-blade propeller isgreater ground clearance due to the shorter propeller blades.
Since there are three blades developing thrust, they can be built shorter compared to a 2-blade propeller on the same airframe.
More ground clearance is always a good thing. In the world of long concrete runways, it is nice to think about fewer prop dings. In the world of unimproved airstrips, more clearance may be an operational necessity!
In an aircraft with more than around 300 horsepower, there may be some performance gains. Aviation Consumer reported in a February, 2001 article that300 horsepower is the approximate point when 3-bladed propellers started to confer a performance advantage over 2-bladed propellers.
However, if your plane develops under 300 horsepower, having more than 2 propeller blades usually brings performance degradation.
The increased weight of having 3 blades has to be offset with additional downforce by the horizontal stabilizer in flight, meaning more drag than any additional thrust overcomes.
Some aircraft, like my Beechcraft Sierra, are subject to a prop hub inspection airworthiness directive (AD). Every 500 hours, I have to have an eddy current inspection done. If I changed the hub (including if I installed a 3 blade propeller) I would not be subject to that AD any longer.
Another significantadvantage for 3-bladed propellers is that they are much quieter.
Remember how earlier we discussed how longer propeller blades have faster blade tips? Well, faster tips means more noise – especially if the tips approach supersonic speeds. Propeller noise is one of the greatest sources of noise from aircraft.
In the video below, watch and listen to the Cessna 185 and its 86” propeller spinning at 2,850RPM.
On a 10 degree Celsius day, the tips are traveling at 0.97 Mach. You can tell by the sound alone that the air moving over the top of the airfoil is transonic. It is a cool sound – no doubt! – but could probably really annoy airport neighbors.
Because the blades of a 3-blade propeller are a bit shorter, they have a shorter length to travel per rotation. This means the tips are not traveling as fast.
So, the 3-blade propeller is a bit more quiet, and not just on the outside of the cabin.
A major component of cabin noise is the “power pulses” of air coming from the propeller and striking the windscreen.
The 3-bladed propeller creates more pulses (3 every rotation as opposed to 2) but each pulse is less powerful since the blades are smaller. So, not only are 3 blade propellers quieter on the outside of the aircraft, they are quieter on the inside as well.
Why do some propellers have even more than 3 blades?
You may be thinking, if 3-bladed propellers confer some advantages over 2-bladed propellers, what about adding even more blades?
Let’s generalize – yes, with high-power engines adding even more blades can make sense. More blades means less efficiency, less noise, more ground clearance, and more thrust.
Aircraft designers have to balance design considerations to find the optimal way to translate engine torque into useful thrust.
The C130 Hercules is an iconic aircraft that many of us are familiar with.
When the aircraft was originally built, each engine had 3-bladed propellers. Very soon after the introduction of that A-model, engineers developed a new model with much higher power.
The increase in power meant that more thrust could be created. Well, as was discussed earlier, they did what made the most sense and added a 4th blade to the propeller rather than risk adding length (and reducing ground clearance and generating substantially more noise).
As the engines mounted to the C-130 got larger and larger, 5 and then 6 blade propellers were fitted to match the increase in horsepower to gain more thrust without sacrificing the unimproved field performance of the aircraft and to keep the noise down.
Most large, high performance propeller aircraft have lots of propeller blades. Such large propellers on aircraft this size would have supersonic blade tips and be incredibly noisy, but engineers are clever.
Planes with such huge propellers havespeed reduction gearboxes, which mean that the engine can spin at a high speed, but the propeller tips can stay subsonic – staying in a quiet and efficient speed range.
Without a speed reduction gearbox, propeller tips on large turboprops would be traveling at speeds in excess of 1,000 miles per hour.
You could add even more propellers but there are increased costs and complexity that mean you probably won’t see a 20-bladed propeller any time soon. The most blades we could find were the 14-bladed Antonov AN-70 propeller.
14 propeller blades on the Antonov AN-70. Granted, they are mounted on 2 counter-rotating discs. Image Source.The popular and speedy Socata TBM turboprop with a 5-bladed propeller. Image Source.The iconic De Havilland Dash 8 turboprop airliner with its enormous 160 inch 6-bladed propellers. Blade tips are kept subsonic with a speed reduction gearbox. Image Source
As a side note, in each of the images above you’ll notice that the blades have a slight curve towards the end of each blade tip. There are interesting reasons for this discussed in our article on why some propeller blades are curved.
Final Thoughts on 2 vs. 3 (or More) Bladed Propellers
Most general aviation planes have either a 2-bladed or 3-bladed propeller. If you are considering a propeller replacement or building a home-built aircraft, you may find yourself having to decide how many blades are right for you.
The bottom line is that 2-bladed propellers are longer, louder, more efficient, and less powerful. 3-bladed propellers are shorter, quieter, less efficient, and more powerful.
It’s important to remember that adding more propeller blades typically adds more cost. The difference between a 2-blade and a 3-bladed propeller in acquisition and maintenance cost should definitely not be overlooked.
Weight differences between propellers are another consideration. Propellers with more blades are heavier.
We haven’t even discussed constant-speed propellers. To learn more about this fascinating topic, check out our YouTube video on the topic:
Last but not least, aesthetics are an important consideration. This really explains why many owners of aircraft under 300 horsepower make the switch to a 3-bladed propeller. It also comes down to personal preference whether you prefer the look of a 2-bladed or 3-bladed propeller.
There are some people who simply prefer the look of a 3-bladed propeller and don’t mind losing out on some efficiency and paying more!
Are gliders hard to fly? A glider pilot weighs in.
Gliders are aircraft designed to fly without using an engine. The general principles of controlled flight in a glider are no different from powered aircraft.
With the exception of dive brakes or spoilers the available control surfaces on a glider are the same as powered aircraft as are the inputs from the pilot that move those surfaces. So are gliders hard to fly?
Flying gliders is not very difficult but does take practice. Gliding takes hand-eye coordination skills and muscle memory that the vast majority of student pilots are able to accomplish while working towards their license which requires a minimum of 20 flights and 10 flight hours.
In addition to the basic flying skills you will need to attain as a pilot, gliders possess a few unique challenges that are a main focus of training.
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Challenges Specific to Glider Training
Learning to fly is somewhat similar to driving a car except in addition to speed and lateral movement (left/right), there is pitch and also roll.
While sometimes challenging at first, learning to master these flight characteristics is something the vast majority of students are able to accomplish.
Gliders pose a unique challenge in that they typically do not have their own propulsion. As such, there are a few parts of training that are more difficult than others, such as the length of training flights, launching, thermalling, and landing.
Glider training for the initial glider pilot certificate is not especially difficult.
Difficulty of Gliding Training Flights
The primary training challenge to flying gliders is flight time. This is because you are not typically finding lift to stay up and only have the time it takes to glide from release altitude back to the airfield.
This means that each flight you really only have time to practice a couple repetitions of a skill before you have to set up for landing rather than being able to drill multiple repetitions of a skill to proficiency.
This can sometimes make the flight challenging in that it is fairly quick, but more so the challenge is in the logistical implication. Shorter training flights means you will need more total flights to accomplish the required training.
Powered aircraft on the other hand can have training flights that last for hours and can accomplish many different requirements and provide an opportunity to practice various maneuvers many times in the same flight.
Difficulty of Launching Gliders
Launching a glider presents several challenges for glider pilots. There are a few skills necessary for all launch methods, and some specific to the different launch methods that we will look at.
Maintaining wings level through launch is necessary as most gliders have a single main gear under the fuselage. While some will also have a nose or tail wheel, they are along the fuselage center line and do not support the wings during launch.
A wing runner can help for the first portion of launch, but once speed exceeds what the wing runner can keep up with the pilot must maintain a wing-level attitude.
Dropping a wing once speed is starting to build and the sudden drag associated with the wing tip contacting the ground can result in damage or crash.
For most launch methods the glider pilot needs to be ready for and able to manage failure of the launch system. For pilots of powered aircraft this is similar to contingency planning for loss of power on takeoff, with the added step of disconnecting from the launch rope.
Now we will look at skills necessary for two of the most common launch methods.
Difficulty of Winch Launch
Winch launch facilities use a winch at one end of the air strip connected by tow rope to a tow hook on the glider under the fuselage near the center of gravity (a CG hook). The winch reels in the tow rope pulling the glider forward.
Once the glider has enough speed the pilot enters a steep climb to gain altitude before leveling off to disconnect from the winch.
Winch launch technique is a practiced skill and even licensed glider pilots should receive training on winch launch procedures if they have never used this method previously.
The winch specific skills are maintaining positive rudder control to avoid running over the tow cable at the beginning of the launch, and maintaining attitude control during the steep climb phase of the winch launch.
During the steep climb phase the horizon is not visible when looking forward, so using the appearance of the horizon out the side of the canopy and the attitude indicator is needed to maintain a wing-level attitude.
Difficulty of Aero Tow
When towed up by an airplane a glider pilot needs to be maintaining their own safety as well as that of the tow pilot. This most significantly begins when the glider first lifts off.
The glider, typically having better performance/lift characteristics than the tow plane will want to fly before the tow plane. If the glider climbs too high initially this can pull the tail of the tow plane up while the tow plane is still on or close to the ground leading to a prop strike for the tow plane.
Once the tow plane and glider are airborne, maintaining ideal position behind the tow plane is the primary task of the glider pilot. This helps the tow pilot maintain appropriate control, and for the glider pilot avoids the turbulent air wake from the tow plane.
Once at the desired release altitude the glider pilot pulls a release disconnecting the glider from the tow rope. The tow plane and rope should be watched until clear of the glider flight path.
Difficulty of Thermalling in Gliders
Since gliders usually don’t have their own propulsion, staying aloft requires pilots to find and utilize thermals and updrafts of air to provide altitude gains to prolong the flight.
This requires some physical ability but more so an understanding of weather theory.
Knowledge of regional weather patterns and terrain features that result in lift makes finding lift easier. There are also indicators that are taught during training.
Ridge and wave lift tend to be larger areas of lift that can be more consistent in their presence due to their dependence on geography or regular weather patterns.
Thermals are rising columns of air formed when the ground is heated by the sun leading to the air immediately above the area being heated & rising often several thousand feet.
Typically thermals will lead to cumulus cloud formation which can help glider pilots identify possible lift sources. They are typically less consistent in location and duration compared to ridge or wave lift and often the area of lift is smaller as well.
The basic description of a thermal conjures the image of air moving straight up like an elevator shaft. That is seldom the case as winds and other factors can cause the thermal to drift from the point of origin on the ground.
Learning to identify the likely origin point and visualize the path the rising air follows is a skill that comes with practice.
A constant focus of glider pilots is locating and utilizing thermals to provide lift for the aircraft to keep it aloft.
Difficulty and Importance of Coordinated Flight in Gliders
Maintaining coordinated flight is one of the most important fundamental skills pilots learn. It essentially means keeping the centrifugal force of the aircraft in line with the direction of the aircraft itself, and is most important during turns.
Uncoordinated flight results in slipping or skidding turns which can be potentially dangerous. For more reading on this topic, see our article on slipping vs. skidding turns.
Maintaining coordinated flight and developing a “feel” for it is very important during thermalling. This is because thermalling is one of the busiest times for a glider pilot.
Thermalling requires maintaining correct air speed, monitoring rate of climb, traffic avoidance, and maintaining bank to stay in the lift.
Thermalling is typically performed at the glider’s best lift to drag (L/D) speed. The best L/D speed for a glider is the speed at which it creates the most lift and the least drag, and is specific to that glider and published in the manufacturer’s handbook.
This speed is often not very much above the stall speed for the glider. Combined with the bank angle (which increases the stall speed) this makes thermalling a maneuver that can result in an accelerated stall. If this occurs when flying uncoordinated a spin can occur.
While a general “feel” for the glider’s energy and coordination is not a substitute for instrument checks, it gives pilots the ability to more quickly interpret the information on the instruments and is something most glider pilots consider an essential skill.
The Difficulty of Landing a Glider
Pattern procedures and approach to landing in a glider are not complicated. The main consideration is there is not an option for a go-around for balked landings.
Glider runways typically have sufficient length to allow for pilots to overshoot their intended touchdown point without incident. That does not mean it is OK to be sloppy with intended touchdown points.
Well executed approach and accurate touchdown become very important for off field landings. This can happen often in glider flying and is referred to as “landing out”.
When landing in a rural field, an accurate approach and touch down can mean the difference between landing without incident, or hitting a fence or tree line. As a result every landing should be used as an opportunity to practice precision, requiring excellent energy management skills.
The Overall Difficulty of Flying Gliders
So now that we’ve looked briefly at some of the unique challenges required to safely fly a glider, are gliders hard to fly? In the opinion of this glider pilot: not especially.
The training required to earn a glider pilot certificate ensures you are able to safely operate a glider. Practice and proficiency in the skills discussed in this article are part of what will make you a good glider pilot.
Like any skill, mastery of the challenges discussed here requires regular practice to maintain proficiency. Flying gliders hoans skills that apply to all pilots and can be incredibly fun; but no, gliders are not hard to fly. They do however, like any other skill, take practice to fly well.
Private, Commercial, and ATP Pilot Certificates Compared
There are different types of pilot’s licenses or “certificates” which grant different privileges and responsibilities. Common certificates to receive are a private pilot certificate, commercial pilot certificate, and airline transport pilot (ATP) certificate. So what’s the difference?
The private pilot certificate allows you to operate an aircraft for personal transportation. A commercial pilot’s certificate allows you to be hired for your flying. An airline transport pilot (ATP) certificate allows you to fly as a pilot for airlines.
These certificates must be earned in order and each requires a progressively higher level of pilot skill and experience, medical fitness, and strictness in operations.
In this article we will discuss the requirements, limitations, and privileges of each of these pilot certificates. This article will discuss only those requirements relevant to pilots in the United States.
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The High-Level Differences Between PPL, CPL, and ATP
The differences between the private, commercial and ATP certificates may seem complex. The table below summarizes the important differences between these ratings.
Medical Requirements
Experience Requirements
Instrument Rating
Privileges
Private Pilot
3rd Class
40 hours
Not required
PIC of aircraft for personal transportation
Commercial Pilot
2nd Class
250 hours
Not required (with restrictions)
Fly for hire
Airline Transport Pilot (ATP)
1st Class
1,500 hours
Required
PIC of airlines
As we will be discussing the Federal Aviation Administration (FAA) Federal Aviation Regulations (FARs) in this article, let’s start with a quick reminder on some of the relevant parts of the regulations. The links below will take you to some of the most important and relevant sections of the FARs.
Becoming a private pilot is an exciting and challenging accomplishment. For most pilots, this will be the only certificate they ever earn. Knowing the rules and limitations of your private pilot certificate is very important.
Private Pilot Certificate Experience Requirements and Privileges
Your first step along your pilot journey will be to earn your private pilot’s certificate. Earning a private pilot certificate requires (among other requirements)40 hours of flight time and passing a written exam, oral exam, and practical exam.
Once you have achieved your Private Pilot Certificate, you will be operating under FAR Part 91 – and this gives you a lot of freedom. Generally speaking, you can fly where you want, when you want, and with whom you want.
The biggest difference you will notice between being a student pilot and a private pilot is that you can carry passengers and don’t need endorsements to visit any new airport you choose to.
Private Pilot Medical Requirements
There are several medical requirements you will need to meet to become a pilot. Although it would be great if everyone who wanted to pursue flying could become a pilot, these medical requirements exist to ensure your safety and the safety of those on the ground.
The Third Class medical examination is an examination conducted by a medical doctor with special training in aviation medicine, an “Aviation Medical Examiner” (AME).
The AME will test your vision (at least 20/40 vision and color vision), hearing, pulse, blood pressure, and other factors.
You will also fill out a questionnaire that asks about medicines you take, drug and alcohol use, and mental health conditions. It is critical you answer the medical exam questions honestly – both for safety and legal purposes.
It’s a good idea to make sure you are medically fit to fly before investing a large amount of money in flying lessons. If you have any doubts or questions, contacting your local AME would be a good place to start.
You can call your local Flight Standards District Office (FSDO) and ask them for local AME’s in your area.
Private Pilot Certificate Limitations
The private pilot certificate does come with several limitations. Keep in mind these rules are in place for your safety and the safety of the flying public.
The main limitation of a private pilot certificate is that you cannot fly for hire.
However, you can split costs of flying (airplane rental costs, fuel, landing fees, etc.) with passengers if you are traveling somewhere together. If you want to take a few friends along for a fun weekend trip, airplane camping or sightseeing, don’t be shy about splitting costs with them.
It’s important to be careful with this rule though.
It would be against the law, for example, to make a Facebook post saying “I’m flying to Las Vegas this weekend, for $100 of gas money you can tag along in my Cessna!” as this would be considered “holding out” your services to the public.
“Holding out” is an important term used by the FAA that you’ll want to familiarize yourself with as a private pilot.
The important point here is to protect the public against private pilots, who have less strict rules and are often less experienced, from having a financial incentive to provide aerial transport services.
One important exception is that it is permissible to use your private pilot license for personal business use. If you have a job with a wide area of operation, for example, it is perfectly allowable to use a plane to reach clients or meetings.
The rules about private pilot flying may seem complicated, however usually common sense is enough to keep yourself out of trouble with “not for hire” limitations of the private pilot certificate. Don’t offer your piloting as a for-hire service and you should be in the clear.
If you decide that you do want to be compensated for your flying, that’s great! It’s time to think about getting your commercial pilot certificate.
Before we end the conversation on the private pilot’s certificate, here are a few more articles on the topic in case you’re looking for additional information:
A commercial pilot certificate is the next step in your flying career and comes with additional responsibilities and privileges compared with the private pilot certificate.
As a commercial pilot, you can fly for hire. You may find it a little tricky to get a high-paying flying job with little experience, but it is a huge change from paying high costs for every flight hour like you would have to up to that point.
One of the most common jobs for commercial pilots is to become a certificated flight instructor (CFI). This requires another certificate and is often the first rating a new commercial pilot will attain. This article discusses how much you will be paid as a CFI.
If you don’t want to go the CFI route, you have several other good options. You could find a job being a skydiving pilot, hauling cargo, banner towing, or doing aerial surveying, to name a few. Keep in mind that as a low-time commercial pilot, you may have to be flexible with working hours, and where you live.
A skydiving job can also be a good way to build valuable turbine time by flying equipment such as the Cessna 208 Caravan, a common skydiving plane. Image Credit.
Commercial Pilot Certificate Experience Requirements
Getting your commercial pilot certificate is a significant step up from being a private pilot. The basic requirements for a commercial pilot certificate are 250 hours of flight time, 100 hours as pilot in command, and 50 hours of cross country time. Also, you must be 18 years old. Just like the private pilot certificate, this can be accomplished through a private instructor (FAR Part 61) or flight school (FAR Part 141).
Getting your instrument rating will be a very important factor in getting hired and is a logical step between your private pilot certificate and your commercial pilot certificate.
Just like the private pilot certificate, you will have to pass a written, oral, and practical test to become a commercial pilot.
Commercial pilot maneuvers in the practical test are more demanding than those required of a private pilot and will require careful practice.
Once you have passed your commercial pilot checkride, you can get your first job as a pilot.
Some of the most common jobs for low-time commercial pilots are CFI (requires another certificate), cargo flying, being a ferry pilot, giving aerial tours, and flying skydivers.
Some smaller air carriers might hire you with only a commercial pilot certificate but most will require you to have your airline transport pilot certificate, which we’ll discuss later in this article.
Commercial Pilot Certificate Medical Requirements
Because you are able to offer your flying services for hire to the public, there is a higher standard of medical fitness required for the commercial certificate than the private pilot certificate.
For example, your vision must be better. You need 20/40 vision for a Third Class medical certificate (private pilot) but you need 20/20 vision for a Second Class medical certificate.
A chart used to determine visual acuity. Image Credit.
The largest difference between the Third Class medical certificate for private pilots and the Second Class medical certificate is that you need to be examined more frequently.
A Second Class medical certificate required to exercise the privileges of the commercial pilot certificate must be renewed every 12 months. A Third Class medical is required only every 60 months if you are below the age of 40, and every 24 months if you are above the age of 40.
This ensures the safety of the flying public – more frequent and more thorough examination by an AME protects the public by ensuring medical issues that could affect the safety of flight don’t go unnoticed.
An important note here is that you only need to maintain your Second Class medical certificate to exercise the privileges of your commercial pilot certificate.
For example, if you can’t pass your Second Class medical examination for some reason but can still pass a Third Class medical examination, you can still fly as a private pilot.
Commercial Pilot Certificate Limitations
Having a commercial pilot certificate means you can fly for hire, but this does come with certain limitations. Let’s say a friend approaches you, a commercial pilot, and asks “Hey, you have a plane… could you fly me to Seattle next weekend? I’ll pay you two hundred dollars.”
This would definitely not be allowed with only a commercial pilot certificate. On the other hand, if they own the plane, it would be allowed – it’s not your plane, you’re just the pilot. More on that later.
To offer both a pilot and a plane for payment hire, you need to be an “air carrier”. This comes with stricter maintenance, equipment, crew, and airworthiness requirements. You would also need to be approved as an air carrier by your local Flight Services District Office (FSDO).
Again, the reason here is to protect the public. Air carriers have stricter requirements in areas like maintenance, crew rest, and required equipment on the aircraft.
You can fly passengers for compensation with a commercial pilot certificate under certain scenarios.
Let’s say a specialized construction company owns a Cessna Stationair that they use to transport highly skilled laborers from their headquarters in Boise, ID to locations around the Mountain West.
You could fly this plane for hire with passengers onboard. The important difference here is that you don’t own the plane.
Cessna Stationair. A CFI friend of mine flies this plane to move workers around for a construction company. Image Credit.
When in doubt, remember the 3 P’s: if you are offering a Pilot, a Plane, and a Price, you need an air carrier certificate.
However, just because you have your commercial certificate does not mean you can get a job at American Airlines flying a jumbo jet to Fiji for a six figure salary – sorry!
To fly for the airlines, you will need to build many more hours and work up to your Airline Transport Pilot (ATP) certificate.
Airline Transport Pilot Certificate
The Airline Transport Pilot certificate is the highest pilot rating available in the United States. To act as the Pilot in Command of a major airline in the US, you need an ATP certificate.
Because of the high level of skill, knowledge, and responsibility required to operate an airliner, the ATP rating has even stricter requirements (stricter tolerances in flight maneuvers, a higher standard of medical fitness, and higher experience requirements) than a Commercial Pilot certificate.
Typically, you will need an ATP rating to act as pilot in command of a scheduled air carrier.
Technically, there is no minimum size for an airline. For example, Grant Aviation is an Alaskan airline that operates planes as small as the piston powered propeller-driven Piper PA-31-350 Navajo as a scheduled airliner, requiring an ATP for pilots.
Grant Aviation operates the Navajo in the Aleutian Islands, flying out of Cold Bay and Dutch Harbor, to places like King Cove, False Pass, Akun Island and Nikolski.
A Piper Navajo can be used as an “airliner”, requiring an ATP. Image Credit
The most common way to build these 1,500 hours is to be paid as a commercial pilot.
Even if it cost you only $100 per hour to build hours, it would cost a whopping $150,000 to build the experience required for an ATP. For most people, it’s unrealistic to pay for all these flight hours and it makes much more sense to be paid for the hours.
Unlike the commercial pilot certificate, being instrument rated is mandatory to attain your ATP certificate.
Just like the private and commercial certificates, you will need to pass a written exam, an oral exam, and a practical exam to attain your ATP certificate.
ATP Certificate Privileges
Because the ATP certificate has the highest experience requirements, you can take on some of the biggest responsibilities in aviation.
Airline Transport Pilots can serve as the Pilot in Command of the biggest jets in aviation, transporting hundreds of passengers. If you dream of flying some of the most iconic jets in the sky, you will need to attain your ATP certificate.
Being an ATP and flying for the airlines is also one of the most lucrative careers you can attain in aviation. However, remember that paying for all the prerequisite certificates is likely to set you back tens of thousands of dollars. Also, depending on how you build time to 1,500 hours you may have to weather years of low pay.
That being said, it’s not unheard of for airline pilots to make six figures after a few years. With decades of seniority at a major airline, you could make even more money and operate some of the most impressive equipment in the world.
Boeing 787 Dreamliner – With an ATP certificate and lots of experience, you could fly some of the most advanced jets in the world. Image Credit.
ATP Certificate Medical Requirements
To hold an ATP certificate and operate as Pilot in Command of an airliner, you will need to hold a First Class medical certificate from an Aviation Medical Examiner. The requirements of the First Class medical certificate are slightly more demanding than the Second Class medical certificate.
If you are applying for a First Class medical certificate, you will need to pass the requirements of the Second Class medical examination and also pass an electrocardiographic (EKG) examination of the heart.
The high medical standards of airline flying mean you must pass an electrocardiographic exam (EKG). Image Credit.
As mentioned in the commercial pilot certificate medical requirements section, if you ever can’t meet the standards of a First Class medical certificate, you can revert to a “lower” medical certificate and still exercise the privileges it grants.
For example, imagine you retired from your job as an airline pilot but still wanted to give flight instruction. In this case, you would only need to meet the requirements of the Second Class medical certificate. If you just wanted to fly as a private pilot, you would only need to hold a Third Class medical certificate.
Difference in PPL, CPL, and ATP Summary
Many pilots only ever get their private pilot certificate. Some others may seek every rating they can and build tens of thousands of hours in an airline career. Being a pilot is all about good planning – for example, flight planning, financial planning, and goal setting.
Whether you need 40 hours, 250 hours, or 1,500 hours, you’ll want to make sure you know all the relevant requirements and be able to plan accordingly. Once you earn each progressive pilot certificate, it’s important to know what is allowed and what your responsibilities are.
If you are ever unsure whether your certificate allows you to fly a certain flight, it is a good idea to review the FARs. If you’re still unsure, you could ask a more experienced pilot, a flight instructor, or call your local FAA Flight Services District Office (FSDO).
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