Skip to main content
31 votes

Why aren't all fighter jets' engine intakes on top instead of forward?

When the inlets are on top, the air entering the engine must make a 90 degree turn to get into the engine. This will cause inefficiencies and might cause massive separation -- which would be very bad....
Rob McDonald's user avatar
  • 12.5k
27 votes
Accepted

How does the Yak-130 fly with blocked engine inlets?

The inlets are closed in order to avoid FOD (foreign object damage) when taking off from unprepared fields. Anyway when the main inlets close, above the fuselage two other inlets open, as visible for ...
sophit's user avatar
  • 12.8k
26 votes
Accepted

Is there an aerodynamic reason for airship fins to be at the tail?

Yes. With fins in the middle the airship would be impossible to control. In order to work, fins need a lever arm with respect to the center of gravity. The longer, the better. Almost all air vehicles ...
Peter Kämpf's user avatar
23 votes

Why a kite flying at 1000 feet in "figure-of-eight loops" serves to "multiply the pulling effect of the airflow" on the ship to which it is attached?

The giant kites mentioned aren't the quadrilateral kites kids fly. They are airfoil shaped parachutes with open noses that generate lift as they move through the air. Ram air pressure inflates them ...
Pilothead's user avatar
  • 20.2k
21 votes

Why aren't all fighter jets' engine intakes on top instead of forward?

Forward-facing intakes provide ram air compression, which convert airspeed into additional pressure. This significantly improves engine performance if there's any significant airspeed. It's true that ...
Therac's user avatar
  • 27.4k
21 votes

If a Cessna 172 is dropped from the sky, what minimum altitude is needed to safely land?

Minimum altitude is 0 ft: simply release the plane and let it sit pretty on the ground. Call it cheating, but it fits the scenario perfectly. If you want it high in the air, what probability of ...
Therac's user avatar
  • 27.4k
20 votes

If a Cessna 172 is dropped from the sky, what minimum altitude is needed to safely land?

Not much in principle. In freefall, the 172 would reach its stall speed in a little over a hundred feet. You'd need to make sure to get the nose down as soon as possible. Then you need to gain a ...
Chris's user avatar
  • 15.9k
16 votes

Why do newer engines have such wide fan blades?

The improvement in efficiency has two roots: Higher turbine pressure ratios. While the very early turbojets managed just 3.14:1, the most recent civil turbofans run at 50:1. Higher bypass ratios. The ...
Peter Kämpf's user avatar
16 votes

Why single engine turbine helicopters can operate on higher altitudes than multi engine helicopters?

Engines are heavy. There is no market for a high altitude helicopter. Airliners fly high up because it lets them reach the destination quickly and cheaply. Helicopter buyers want to fly slowly near ...
Anonymous Physicist's user avatar
16 votes

Why are supercritical airfoils not used in GA aircraft?

Because supercritical airfoils are designed for the transonic regime of flight speeds, which GA aircraft do not operate in. Many other considerations, such as flutter, limit GA aircraft speeds even in ...
p8l's user avatar
  • 161
15 votes

why stabilator has a lower travel limit for down movements?

Most aircraft can handle higher positive G loading than negative, which allows more "up" stabilator than down. Also, most aircraft center of gravity limits are such that the stabilator has ...
Robert DiGiovanni's user avatar
14 votes
Accepted

Why is a flat turn less efficient than a coordinated turn?

I don't believe Chris's answer is incorrect, however I'd like to pose an alternate way of explaining what happens: As you have noted, turning requires a horizontal force perpendicular to velocity, and ...
ThatCoolCoder's user avatar
14 votes

Why does this curved wind tunnel rotate?

While superficially similar, this curved windtunnel solves a very different problem from a straight windtunnel. A straight windtunnel is used to study steady flight without needing a very long ...
Sanchises's user avatar
  • 13.4k
13 votes
Accepted

How to slow down while maintaining altitude

To maintain altitude, lift must be equal to weight. The first question is, does slowing down reduce the amount of lift we have? We can look at the lift formula for the answer: $$\mbox{Lift} = C_l \...
Ben's user avatar
  • 14.5k
12 votes
Accepted

Can the use of flaps reduce the steady-state turn radius at a given airspeed and angle of bank?

No. ... claim that, at a given airspeed and bank angle, having the flaps lowered will decrease the turn radius. This claim is nonsense. For a coordinated turn, bank angle and speed alone are ...
TypeIA's user avatar
  • 14.4k
12 votes

Why a kite flying at 1000 feet in "figure-of-eight loops" serves to "multiply the pulling effect of the airflow" on the ship to which it is attached?

Have you ever flown a dual line kite? If you keep it steady it will climb until it reaches a steady state and until it is mostly horizontal and only pull minimally on the lines. If however you turn it ...
ratchet freak's user avatar
12 votes

Why does a flat plate create less lift than an airfoil at the same AoA?

It shows that at the same positive AoA, a flat plate generates less lift compared to the NACA airfoils. From an arbitrary guess, the lift force generated should at least be the same for both Your ...
sophit's user avatar
  • 12.8k
11 votes

Is it feasible for an individual with limited current knowledge to undertake the development of an aircraft from scratch?

It's not possible to solo-develop a 9-12 seat airplane to a legally flyable condition. The authorities want passenger aircraft built by people who know what they're doing, then checked again by ...
Therac's user avatar
  • 27.4k
11 votes

Why aren't all fighter jets' engine intakes on top instead of forward?

Takeoff is only a small part of the flight regime. And not necessarily the most demanding. A high G turn , where the inlet on the top of the wingroot is in the shadow of the airflow...air intake is ...
WPNSGuy's user avatar
  • 9,037
10 votes

Is turbulence a random process?

The equations that describe fluid flow, the Navier Stokes equations, are generally considered chaotic. In particular turbulence is defined as " fluid motion characterized by chaotic changes in ...
DJClayworth's user avatar
  • 4,502
10 votes

How do canards reduce the X-59's sonic boom?

One of the important factors for sonic booms is the longitudinal distribution of lift along the aircraft. The canard helps bring some of that lift very far forward. Notice also that the aircraft has ...
Rob McDonald's user avatar
  • 12.5k
10 votes
Accepted

Why are supercritical airfoils not used in GA aircraft?

Actually, Whitcomb's GA airfoils were based on experience gained with supercritical airfoils. They share the large leading edge radius and the strong rear loading with them. Other than that, ...
Peter Kämpf's user avatar
9 votes

Why does the nose pitch up during power reduction in a T-tail with rear mounted engines?

The engines are mounted above the vertical center of gravity position. That means there is a vertical moment arm from the thrust which causes a pitch down when thrust is increased and a pitch up when ...
Jan's user avatar
  • 2,398
9 votes
Accepted

How does the horizontal component of lift when flying at a bank angle cause the aircraft to follow a circular path?

You are absolutely right that the horizontal force perpendicular to the direction of flight cause a side slip. The rotation comes from the vertical stabilizer which as soon as a side slip occurs ...
DeltaLima's user avatar
  • 83.5k
9 votes

Why weren't WWII piston aircraft able to fly at 500mph?

What am I missing? The contribution of zero lift drag to overall drag at high speed. L/D drops to much lower values than 10 at the top speed of piston-powered airplanes. Let's take an example: Given ...
Peter Kämpf's user avatar
9 votes

Why does this curved wind tunnel rotate?

Here you'll find his paper about the wind tunnel. Apparently the rotation has been introduced in order to compensate for the Coriolis effect.
sophit's user avatar
  • 12.8k
9 votes

Why does turbulence over a wing make drag?

Short answer: turbulent flow causes vigorous mixing of the flow nearest the wing with flow further away from the wing. this tends to share the energy imparted from the wing to the airflow nearest the ...
niels nielsen's user avatar
8 votes

How can flow in the compressor of a jet engine go back to the inlet?

Note that the flow speed past the diffusor (which sits between the compressor and the combustion chamber) is very low in order to allow air and fuel to mix, the fuel to evaporate and the mixture to ...
Peter Kämpf's user avatar
8 votes
Accepted

Why do newer engines have such wide fan blades?

Fan blade evolution The historical fan blade had the same form as a compressor blade, Figure 3 and 4. The weight of the solid titanium blade stopped a wider cord design. The long and slender shape ...
user3528438's user avatar
  • 2,910

Only top scored, non community-wiki answers of a minimum length are eligible