New answers tagged

1

Without entering into details of aerodynamics: The weight of the aircraft must be balanced by lift so altitude can be maintained constant. Lift can be increased or decreased a bit when it's necessary to climb or descend. For many problems, weight can be seen as acting at the center of gravity, even if weight isn't actually a single force acting at a single ...


3

The position of the wing is determined by many things, but primary among them is an analysis of the distribution of the weight of the aircraft. Aircraft remain stable in flight because there is a balance of moments (that is, the nose up/nose down rotational effects of the forces generated by the airflow over every part of the aircraft). The total moment ...


3

"Were it not for the wind, flying would be so easy" The root issue with any "high lift" design is cruising airspeed. The main advantage of commercial air travel is time savings. Drag increases with V$^2$. As airspeed increases, drag from forward motion becomes much greater than drag from lift. Airships (blimps or zeppelins) are most ...


0

Yaw dampers prevent dutch roll on swept-wing aircraft. A single-engine propeller GA aircraft with a straight wing has no need for a yaw damper, since it has good directional stability and doesn't have a tendency to develop dutch roll like a swept-wing aircraft does. Dutch roll is when the tail of the airplane “wags”/moves left and right as the wings roll.


3

Yes. The structure that joins the engine mount to the wing, nacelle, pylon, or whatever, has to transfer all of the forces being produced by the engine and propeller or fan, and their mass, to the wing box, and these forces are certainly present in cruise flight. So you have the thrust of the propeller/fan applying a tension load forward pulling the ...


1

A Magnus Effect airship, the LTA 20-1, was developed and a scale model tested by a company, Magnus Aerospace Corp, in Canada back in the early 80s in Ottawa. Read about it here. I remember that it got a fair amount of publicity in the Canadian aviation press at the time.


6

Wobble pumps are manually operated boost pumps and are normally upstream of the engine driven pump, often used to help prime it by pre-pressurizing the engine pump inlet before starting. The DeHavilland Beaver had a wobble boost pump as the sole backup pump, which you would use to build fuel pressure before starting, and if the engine pump quit, you could ...


5

Regarding small aircraft, I had an experience this morning that shows why a pressure gauge is useful. On the right tank, I was in the center of the green arc without the boost pump. On the left tank, though, it was at the low end of the green arc. Technically still okay, but I felt safer leaving the boost pump on when using that tank. More importantly, I ...


11

If your fuel system has pumps, a pressure gauge is important because it provides a precise status of the pump and can provide early warning of future problems, like pressure fluctuations, or declining but still acceptable pressure. A warning light is there to get the pilot's attention when things really go south. In an ideal world, you'd want both, but of ...


21

Much depends on your specific aircraft. Some have a need for fuel pressure values, others don't. Likewise fuel temperature readings. On the 737, there is a light as you describe next to each fuel pump switch, linked to a sensor just downstream of the corresponding fuel pump. If the light's on, the pressure is low and the pump should be turned off because ...


1

Horten Ho 229 used "drag rudders" at the tips of the wing to control yaw: Source These devices are in the family of airbrakes, they create drag, not to be confused with spoilers which destruct lift.


4

Turbulence intensity applies to the air around the aircraft. The sustained load factor applies to the aircraft itself. These are apples and oranges, one cannot be directly compared to the other. In a simple model of a high-G turn, the air remains stationary, and the aircraft increases its lift N times. Thus its wings have to be designed to carry a load of N*...


1

My question boils down to: how an aircraft can withstand very high momentary forces but not very high sustained forces. From your question one can gather the maximum manuvering load factor has remained the same, and the turbulence intensity for design criteria has almost doubled. How is it possible? Fiber reinforced composites. These materials can ...


4

As drag decreases as AR increases & lift also decreases as AR increases, so the Aerodynamic Performance (L/D) decreases. Why should lift also decrease? You should keep wing area constant, so lift should also stay constant. This translates into increased L/D. Generally, an aspect ratio increase has these consequences: More wingspan, so induced drag will ...


1

Frontal drag increase, which is not very important on low speeds, but increases dramatically on higher speeds. Construction weight and resillience - the longer wing, the lower strenghts it can carry. So the long wing is good choice for relatively slow glider (low induced drag - low strenghts and little resillience required), but for higher speeds the cost ...


17

The normal airspeed indicator (showing indicated airspeed, IAS) only has one needle: The IAS indicator (US-1600) shows Indicated Air speed up to 1600km/h. It has one needle (2) and one window (1). This window will show “1” when IAS is >1000km/h. I think you mean the Mach meter, which is combined with a TAS (true airspeed) indicator: Thick needle 1 ...


5

It might have something to do with the super stall phenomenon in which a stalled wing blankets a T-tail.


3

Some dimensions (Source) Notice that the cabin cross-section at seat location is closer to rectangular than circular. (Source) So the interior cabin width is 105 cm, 42" at seat location. That is 3' 6". I guess the seat squabs are around 18" wide. According to Wikipedia concerning commercial airline seats: Since the beginning of the 21st ...


13

A horizontal tail on top of vertical tail would require strong and heavy structures, which in turn is not good for economics of flight. The bigger the plane is, the more challenging the loads the tail has to handle are, so what might be a feasible solution on a regional jet might not work at all for a large jet. T-tails are an obvious choice when the ...


-2

I have read somewhere that there is only one company that manufactures CRT screens now and CRT screens will have to be replaces at some time in the future because there will be no spares. I think work is in progress to certify them.


2

My understanding is that the lift fan (two sets of contra-rotating blades) is driven from the main engine via a permanently rotating drive shaft, but that the drive from the shaft to the lift fan is connected/disconnected from the lift fan via carbon clutch plates. In conventional flight it makes little sense to waste engine power driving the lift fan when ...


3

The tendency is to mount the engines as close to centerline as possible. This mitigates control problems in engine out situations and keeps the wing structure as light as possible: if engines were far from the centerline, the structure of the wing would need to be stronger and thus heavier, and should either/one of the engines fail, the running engine(s) ...


4

The Cessna 210 Centurion has a maximum cabin width of 3’8” or 44” or 112cm. It is actually one of the larger single engine Cessna piston powered aircraft. The very popular Cessna 172 only has a 3’4” or 40” or 102cm cabin width. Yes, the seats are very narrow but I can’t find any exact measurements.


1

Since mounting the engines up high makes them more difficult for mechanics to service and inspect, you would want to have a good reason for putting them there. It sounds like Embraer's reason is sound (and that fact that their entire line and assembly and design process is based on aft-mounted engines). I cannot cite any evidence for this hearsay claim, but....


2

I estimate a 565 or 567" chord length where the wing meets the fuselage and wing-to-body (WTB) fairing, based on the Fuselage Station Diagram from the Structural Repair Manual: https://static.rcgroups.net/forums/attachments/1/8/4/2/1/0/a5165653-56-img063%20-%20Copy.jpg I would subtract 20" to account for the curvature at the leading edge where the ...


1

Fuel efficiency is very important for transport bottom line profit, which is why wing mounts are generally seen. A number of ex-passenger liners such as the Boeing 767 are re-purposed as cargo converts. The Embraer concept moves them back for cabin noise mitigation, but rear mounts give back a little efficiency because a father rearward CG shortens the tail ...


2

https://en.wikipedia.org/wiki/Propfan#1970s%E2%80%931980s That Wikipedia page has a good analysis of propfans a.k.a. unducted fans. See the MD80 testbed and reference to various designs (e.g. Boeing 7J7 slated to be the 737 replacement) with rear-mounted propfans. While not coming to fruition evidently it was considered to be a possible alternative to ...


4

TLDR: Pretty much impossible with current technology as I understand the question. I think you are focusing on the wrong part of the problem. Turboprop vs turbofan is pocket change compared to the amount of rocket fuel required to get to orbit. Let's put some numbers to it. I'm assuming the following mission 1) Deorbit from low earth orbit, 2) landing (...


24

There are two really big issues with tail mounted powerplants with propellers; weight distribution and Foreign Object Damage. Tail mounted engines move the empty C of G aft. This forces you to put the disposable load with a forward bias to compensate, hence the long forward fuselage necessary to put the loaded C of G in the required range. Of course, when ...


8

As stated in comments and Dave's answer, it has been done, but I'm guessing you were thinking about mass produced (successful) commercial passenger planes. Here are a couple of reasons: The propellers on a passenger plane need to be quite big, so they would, for clearance reasons, need quite long and thus heavy pylons. Weight in the tail of a plane is ...


12

You can make a case that this was the original way to build airplanes as the Wright Flyer had a forward elevator and rear-ish mounted props extending off the back of the wings. Other than that there have been many designs to incorporate rear propellors. The Bede BD-5 has a rear prop. Burt rutan built various designs with rear mounted piston engines/props. ...


1

The F-35 Lightning has an approach to VTOL that is similar to what you are requesting. There is a propeller (strictly speaking, a ducted fan) pointed straight up in the middle of the fuselage and has doors that open above and below it. It is powered by the jet engine and used during vertical takeoff and landing.


0

Any VTOL arrangement will put a lot of blast on the landing surface, so a practical, off the shelf solution would be the Pratt & Whitney J58 hybrid turbojet/ram jet to get you off the ground and into near space at around Mach 3, before switching to rockets. Although it is possible to mount a prop on this type of engine and fold it, drag and turbulence (...


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