# Tag Info

## Hot answers tagged propeller

61

That is crazy. DON'T just rely on an person who's new to airplanes and only training is 5 minutes of showing them what to do, who may or may not react correctly when it springs to life, as the only thing preventing the plane from heading off somewhere while you try to dive clear. Don't. Do. It. Tie the tail. To something. Anything. Use the passenger and ...

22

I’ll second John K’s answer. Do not attempt to hand prop an airplane without receiving professional instruction on how to do it safely. It is a real easy way to get seriously injured or killed, as this idiot almost found out. It should also involve two competently trained people, one to do the hand propping, and the ...

22

Yes to some degree. It depends on the idle rpm, prop pitch, engine compression and your gliding speed, but if the engine is off but windmilling, there is substantial drag from the energy needed to windmill the prop without any help from the engine and it will knock some measurable amount off the glide ratio. When it's idling, it might still be ...

12

First propeller use: A highly cambered airfoil would cause high pitching moments and twist the propeller blade. Of course you can pre-twist the blade so it will assume the correct shape in the desired operating point, but a propeller needs to work over a wide range of operating points, from take-off roll to high speed flight at altitude. In off-design points ...

11

The NK-12 engine uses a differential epicyclic (planetary) gearbox. Unlike the typical planetary gearboxes where one of the gears is fixed, here all three parts are moving: the turbine drives the sun, the planet pinion drives the front propeller, and the ring drives the rear propeller. The gear ratios are the same between the front and rear, but the torque ...

10

You are not wrong, it is more efficient to accelerate a large mass by a little than a small mass by a lot. This is due to momentum being linear with speed and mass, while energy is linear with mass but quadratic with speed, so the same momentum can be obtained more efficiently by slowly pushing a large amount of air, e.g. with a large propeller. The ...

10

You can't just cherry-pick aerodynamics and exclude everything else when it comes to aircraft design. But let's entertain flight dynamics alone for this instance, and use Selig S1210 or S1223 as examples. Selig-S1210 (for Re 0.2e6, 0.5e6 and 1.0e6) characteristics: First, notice that the linear range of the airfoil extends from $C_l$ 0.5 to 1.9, which ...

8

According to Diamonds website the NG engine is a: Austro Engine AE 300 turbocharged common-rail injected 2.0 liter diesel engine with 168 hp and EECU single lever control system The prop is a: 3 blade MT hydraulic constant speed propeller features advanced blade geometry for efficient performance, low vibration and noise. It is automatically ...

8

I fly a large 4-engine turboprop. It uses constant speed hydraulic props, which automatically change blade angle to maintain 1020 rpm. The sync box (which I was unable to find a picture of) takes inputs from each engine's tachometer generator (where it gets the RPM signal) and a pulse generator, which is a magnetic pickup right behind the prop. There is a ...

8

The answer to this is a definite "maybe". YouTube personality Trent Palmer tested this very question. He was actually able to glide further with the engine off than he was with it at idle. It was a very small gain, though, on the order of a few seconds extra flying time per 1,000 feet descent. The people he was with reported different results: One guy said ...

5

The difference between a ducted propeller and a turbofan is mainly determined by the difference between a propeller and a fan. A propeller has relatively few blades, which are relatively long and slender. A fan has many blades, with a relatively large chord. Like a household fan. A parameter to catch blade count and chord relative to blade length, is the ...

5

In the second photo is just a "feathered propeller" (flag position or rest position on ground to not be spinning around if the weather is windy). This pitch is not used in flight unless the engine is stopped (not working), in which case the feathered position is required to minimize drag on the aircraft from the propeller.

5

Maybe it is one step before the Gladiator: The Gloster Gauntlet. Here the number of wing struts and the landing gear are a better match. Gloster Gauntlet (picture source) It must be noted that a lot of experimentation went on with those aircraft. The one in the picture above has guns added on both wings which made the aircraft too heavy and were removed ...

5

Fan shrouds are a fix for a problem that can normally be designed around in other, more efficient ways. They do reduce tip loses, but usually the tip loses are smaller than the weight and drag penalty of the shroud. The fundamentals of prop/fan/rotor design is that thrust is proportional to the increased momentum of the air flow, but the power required to ...

5

The term "critical engine" can actually refer to two very different factors: P Factor Engine driven accessories, depending on the airplane and how it's configured. A twin with counter-rotating propellers doesn't have a critical engine from a controlability perspective, but very often there are important engine driven accessories, like hydraulic pumps, ...

5

With my old VariEze (not a training aircraft; in the same power class as the Cessna 152 but lighter and with much higher wing loading) I had a cruise propeller and a climb propeller that I could exchange on the ground with about 30 mins of work. I measured ground roll at max gross weight and calm wind to be around 1500' with the cruise prop and 1100' with ...

4

That makes sense. A Bell 47 helicopter gets way over 3000 lbs of thrust from its 37 ft 300 rpm horizontal "propeller" on only 280 hp (with a chunk of that going to the tail rotor), well over double what that engine can produce turning an 80 inch propeller at 2700 rpm the normal way (maybe 13-1500 lbs thrust). But to use it like a regular propeller would ...

4

The propeller generates thrust to counter drag. Drag is created by both the forward velocity of the plane through air (parasite drag) and as a byproduct of lift (induced drag). Lift is a also a consequence of movement through air and is used to counter weight. The above is mostly true for conventional, heavier than air, fixed wing aircraft in un-...

4

Ian Lemco of the Royal Society published a note on this in 2007. He described the invention more as a jet engine than anything, as it featured a central compressor feeding tip-jet nozzles. Burner position varied during development of the design, from central to blade tip. A patent dating from 1910 shows jet combustion at the tip. One central compressor was ...

4

By modulating the fuel flow to the slave engine, ie the one which is to synchronise to the "master" engine, Note. Limited authority of fuel modulation and not permitted in Take off or approach. One writer alluded to synchrophasing to not only reduce beating bit alos reduce noise, You can as I have done move the point of minimum noise around/along the cabin ...

3

Here's a simple example. Without a propeller, a glider moves forwards and (in calm air) descends very gently. So lift is a result of moving forward. Then, moving forward is a result of pointing the nose slightly down -- or, if the glider has a sustainer engine, a propeller. So the primary purpose of a propeller is to keep the airplane moving forward.

3

According to this ATSB Australia Report, the Original Blade Weight of the Trent 800 Blade that failed was 11.6KG. The weight of the blade in grammes is etched into the blade root. https://www.atsb.gov.au/media/33974/tr200100445_001.pdf Page 9/10. Fan Blades of the same type all differ (slightly) in weight and are chosen specially to balance the engine when ...

3

It depends on the power source. a single piston engine driving both props (as shown in the image in the question): they're geared together so rpm will be the same. two turbines driving one prop each (e.g. Double Mamba): no coupling between the engines, so prop speeds may be different. You could even shut down one engine in flight (for low-speed, fuel-...

3

Most if not all contra-rotating propeller systems are geared together so that both sections turn at the same speed. This is done so that as well as allowing effective conversion of very high power into thrust, torque and P-factor are cancelled, making the aircraft easier to fly (especially in a single-engine or two-into-one installation). This is why you ...

3

As always with these questions it seems to be a religious thing. If you ask 2 people you will have at least 3 different answers and most of them will sound somewhat reasonable. I had the situation that my FIs always taught and asked me to move the planes (taildraggers) with me pulling the plane on the prop and them steering using the rudder. A few days ago ...

3

If freezing rain is expected, put it in + position so one of the spinner's blade exit slots points straight down, to completely drain the spinner to avoid ice buildup therein. If you have a square-tip propeller, don't put the topmost blade exactly vertical, so birds perched on it don't make their acidic poop run down the length of the blade. -- Paraphrased ...

3

Why aren't propellers way larger than they typically are? There are some "propellers" these days with a 400 foot disk diameter, known as windmills. But, they are doing their best to extract energy from the airstream and here lies the issue. "Relative wind" is conveniently used to combine the net direction and force of two aerodynamic effects, but let's ...

3

As a rule of thumb, use fully turbulent flow at the elevated speed of the propeller wake on all surfaces wetted by it. The speed increase will result in higher friction drag compared to the propeller-free case and results in a drag increase that looks about right. A very interesting paper on the efficiency of an installed propeller can be found here. By ...

3

I have seen the movie, but it failed to occupy my memory... anyway: Yes, the A400M propellers are contra rotating, and more specifically DBE as you described. I am not 100% sure, but I'm willing to bet all A400M's ever produced have this configuration. So if the propellers seem to rotate in the "wrong direction" there are two possible causes: it ...

2

I think what you'd ideally want to do is to have a fast-rotating "inner" propeller and a slower "outer" one, or actually a propeller whose RPM gradually decrease from the inside to the outside. Although that would look cool, it doesn't work with non-fluid materials for the rotor :o) So, the next best thing is to have two behind each other, where the ...

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