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82

No. Not a useful propulsion engine. The first problem is power. The air stream from Dyson's fans is weaker than what you can get from a conventional fan the same size, and jet engines need a very powerful stream. You'll notice they're quite heavy as well; Dyson AM-06 has a thrust-to-weight ratio of just 0.06, 100 times less than a jet engine. The second ...

23

It isn't done because a moving control surfaces is easier to design and build than an engine mount that rotates. Plus the associated structure needed to accommodate the thrust, p-factor, and gyroscopic loads is going to be a lot heavier than ailerons, spoilers, moving tail plane, etc. Another issue is if one loses one or both engines, your roll and pitch ...

20

In principle yes. But some details will turn most potential operators off. Noise is the obvious first one. You might not mind, but cockpit noise and vibration in operation will certainly put an unacceptable stress on the pilot. Just think how you will communicate with ATC or with a co-pilot. Also, your choice of airports to operate from will be rather ...

18

Difference between engine types That different engine types cause the optimum loiter speed to be different is due to the amount of air used for thrust creation. Propellers accelerate a lot of air by a little, while jets accelerate a little air by a lot. Thrust is the difference between the exit impulse and the entry impulse of the air flowing through the ...

17

It is essentially two propellers stack on top of each other. You can see it in this picture of a Lazair. As for why they were chosen for the Lazair, Many have asked why Ultraflight opted for double propellers stacked in a biplane fashion. This is a very unique setup and draws lots of attention. Apparently when Ultraflight changed over to the Rotax ...

16

there is a lot going on here. Short answer is that a ducted fan (what you have pictured) can produce a lot more thrust (experiments from one paper say twice as much) than an open rotor of the same size. The big thing that these ducted fans have going for them is the fact that tip losses become negligible because there simply isn't room for the tip vortex ...

16

Spraying water into the exhaust stream will cool down the exhaust flow. The energy needed to heat and evaporate the water needs to come from somewhere, after all. The cooler and denser exhaust flow will slow down, so its impulse will become lower, reducing thrust. While the mass flow will go up, its speed will be reduced. Since water enters the flow as a ...

13

Could you create an aircraft using an jet engine/propeller/ducted fan on a gimbal? Sure you 'could'; it is feasible by the laws of physics. But just because you can does not mean that you should. Setting up multiple points of lift on a manned aircraft seems like a good idea with a lot of advantages but is a Pandora's Box of problems, the not the least of ...

12

The thrust of a propeller is proportional to the inverse of airspeed, while the thrust of a pure turbojet is roughly constant over airspeed in the subsonic region. This means that two airplanes with the same static thrust, one propeller-powered and the other jet-powered, will reach very different top speeds. And, no, piston engines are more efficient. A ...

12

Anti-submarine and maritime surveillance aircraft (such as the turboprop P-3 Orion) typically fly slower and lower than the 100+ passenger jetliners. For those speeds and altitudes, a turboprop is more economical. So there is no need that would push such a massive undertaking to retrofit an airplane. See: Which engine is more efficient between turboprop vs ...

11

Yes there are. Although they are not for commercial aviation. One example are solar powered engines: Source Wikipedia Alternatively, there are other means of storing energy - rubber bands, but this one is just for model aitplanes. Source: Pinterest But in either case, you need store energy somewhere, and best way is to use oil-based fuels.

11

A supersonic ram jet (scramjet) requires a fuel with a very high flame speed, so the combustion doesn't take place after the fuel-air mixture has left the engine. Aviation fuel would be completely unsuitable, and only hydrogen gives acceptable results. The low density of gaseous hydrogen, the storage problems associated with cryogenic hydrogen and the ...

11

The thrust variation with altitude would be highly engine specific, but the general trend is nicely depicted in the image below: Read this for further details.

11

At the end of the day both engines have the same task: convert chemical energy to kinetic energy. Not quite. The answer you linked gave away a golden hint. In a piston engine aircraft (I am excluding turboprops now) chemical energy is transferred to rotational kinetic energy, which drives a propeller that transfers part of this rotational energy to the air ...

9

Some airliners have in fact landed more or less successfully using only engine power for control. The 2003 DHL attempted shootdown incident is an example. A major difference between United 232 and Fullerton's landings you cite is that Fullerton was working for NASA testing a system designed specifically for the purpose of assisting pilots in controlling an ...

9

A rocket-powered missile carries both fuel and oxidiser and oxidiser is the heavier part. For example a gram of jet fuel needs almost 3.4 grams of oxygen to fully burn! Increasing the fuel load requires also increasing the power, which means even more fuel and this limits the practical range of a missile. Ramjets are air-breathing, so they don't need to ...

8

This question is pretty close. And you should read here as well as here Generally pulse jets are not great at low speeds (and can be hard to start when stationary). These are key aspects of small GA planes. The noise may not be an issue for you locally (in terms of noise abatements) but it may be an issue for the occupants of the aircraft. In short it is ...

8

Thrust is produced by accelerating air. The exhaust air leaves the engine nozzle at a fairly fixed velocity, so the acceleration is mainly controlled by the difference between the exhaust and incoming airspeeds. The faster the aircraft speed, the less acceleration is being created on the intake air. Therefore thrust decreases with increasing airspeed. In ...

8

Yes, it is. It was used on may 2nd generation designs already mentioned by habu, and it is returning now in the 4.5th generation, now with canards: Eurofighter Typhoon: JAS-39 Gripen: Dassault Rafale: And occasionally without too: HAL Tejas: And most of the other designs, while having horizontal tail surfaces, are not really far from that layout either:...

8

The Skreemr at the present time is only an advertisement idea, so comparisons are not really meaningful. Nevertheless, the difference with the Concorde is the expected range of speeds: at Mach ~2 a scramjet can hardly work (the air would be too slow at the combustion location). All jet engines work on the same principles: compress (and slow down) the mass ...

8

Water injection in the exhaust could work if: The water is fully evaporated before it exits the engine exhaust. The fuel injected in the combustion chamber must also be fully evaporated for effective combustion, and this does take some time end effort - and temperatures in the combustor are higher than in the exhaust. The injected steam counteracts the ...

7

The short answer is: No. One cannot calculate the inlet mass-flow based on the velocity alone. However in order to "know" the velocity ( $v$ ) you most likely would have measured everything you need (see below). Your confusion with regards to the in- and outlet mass-flow might be based on the fact that the intake does not "collect" all air upstream ...

7

Taking the Sukhoi Su-35 for example, it has two engines, each capable of producing 86.3 kN of dry thrust, combined they produce 172.6 kN. With afterburner they produce 284 kN (142 kN each). The jet engine on the American F-22 produces 156 kN with afterburner, close to the 142 kN of the Su-35. Soviet Union / Russia made the Kuznetsov NK-32 military jet ...

7

Many small 4 to 6 seats propeller airplanes can overcome their brake/wheel holding capability, on concrete and ashpalt. My Cessna Cardinal is 180HP, I do engine pre-takeoff runup checks at 1700-1800 RPM. Going to 2600, the plane will start moving. Many other planes of similar size are 300 HP, and they definitely won't hold. We only have two 5" or 6" disc ...

7

Welcome. I'm afraid your theory wasn't actually working. Reducing the duct's exit diameter led to an increase in its internal pressure, increasing load on the propeller, and likely even causing some reverse flow. Nozzle design is a complex subject. I can't think of a way to condense it, even limited to one specific case, into a suitable answer; maybe I don'...

7

The engine mount is an important component that transfers the prop thrust to the airframe. It's clearly visible in this photograph of a fast and powerful plane, a Bf109. Of course, bearings transfer thrust between the rotating and static parts. That is common to all engine-propelled vehicles, ships, cars, planes... The main thrust load, in the picture ...

7

Turbofans already produce much less noise than the turbojets used in the 1960s. In general, the higher the bypass ratio, the lower the noise level. It's difficult to silence a jet engine: any silencer impedes the airflow which means a significant power loss. Noise levels are usually expressed in dB rather than %, a reduction by 90% is a 20 dB difference, ...

6

I don't know the exact answer, but it's on the order of 0.100" (i.e. it's more than 0.010" and less than 1.00"). The more interesting part is that it's not just a simple linear stretching. The blades have a twist to them, and at speed they untwist, which is a strong contributor to the total change in length from 0 rpm to redline.

6

While the pulsejet powered Kawanishi Baika from the WW2 was really far from the GA, from the picture it looks like it was a relatively small plane of very comparable size, capable of taking up under own power, manned. While none were eventually built, seems that the idea was accepted rather seriously at the time. (Its sister ship is the Fieseler Fi 103R, of ...

6

Sure you could, but why would you want to? There's no inherent benefit to be had in vectoring thrust as opposed to using control surfaces. It doesn't simplify things to any extent, it just makes things complicated in other ways. In order to have effective roll control you'd need to space motors out on the wings which could vector in line with the center of ...

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