73
votes
Accepted
Does lift equal weight in a climb?
It depends on exactly how you define "lift" and "weight". You might say intuitively that lift is all the forces acting on the aircraft in the upward direction, like this:
In this case, lift must ...
- 1,063
41
votes
Accepted
Why is this plane struggling to gain altitude?
According to the video's information:
EMB-721 Sertanejo heavy and insane takeoff in Carlos Prates
This is
"EMB-721 Sertanejo heavy and insane takeoff in Carlos Prates.
Full fuel, 6 on board plus ...
- 560
38
votes
Accepted
Can a plane bank without turning?
Yes it can. The steady-heading sideslip (SHSS) maneuver is used in flight testing to demonstrate static lateral/directional stability (similar maneuvers exist as sideslip approach in crosswind, or ...
- 11.1k
34
votes
Accepted
How do "tip jet" helicopters cancel the torque effect of the main rotor?
This is a basic physics question, involving Newton's third law of motion (For every action, there is an equal and opposite reaction.) When a centrally mounted engine applies force to turn the rotor, ...
- 2,587
33
votes
Accepted
Why is the ball no longer centred in a multi-engine airplane with inoperable engine?
Asymmetric thrust means now you have more thrust on one side than the other. A yawing moment results.
You want to balance this yawing moment in order to still fly straight. This means the airplane ...
- 236k
33
votes
Flying upside down without feeling it
This sounds like a barrel roll.
This is a corkscrew-like flight path in which the airplane rotates around an axis between its longitudinal and pitch axes by flying along a path which lies on the ...
- 236k
32
votes
Without wind, would a plane go straight if the pilot let go of the controls?
If the airplane is properly trimmed, the airmass is smooth, and the aircraft is inherently stable in its design, then yes - many airplanes are capable of flying straight with only very light and ...
- 27.2k
32
votes
Accepted
Why do airplanes usually pitch nose-down in a stall?
You are quite close to the answer
And indeed, if the wings stalled before the tailplane, I would expect the downforce produced by the tailplane to be dominant, and the nose to pitch even further up. ...
- 13.7k
30
votes
Accepted
Does a sudden drop of the velocity of the headwind affect the airspeed by lowering it?
Your airspeed does not remain constant because of inertia: it takes more time for the airplane to adapt to the new relative wind, compared to the time it takes for the wind to change.
Example One: ...
- 39.8k
28
votes
Accepted
Do airliners reduce their angle of attack to maintain lift = weight as fuel burns off during cruise?
Yes. As fuel is burned the airplane will want to climb, so the autopilot (which is flying the plane 99% of the time and will normally be in altitude hold mode once you're at your clearance Flight ...
- 134k
28
votes
Accepted
What is a "rapid changes in gravitational force"
The TSIB preliminary findings and the BBC use "G" as a short-hand for g-force, which is not the same thing as "gravitational force". They are using the wrong terminology here.
The ...
- 57.7k
27
votes
Accepted
How do elevons work to roll a flying wing?
Good question! There's a bit of a misconception: when the elevon moves up, it actually decreases lift. It pushes air up which pushes the wing down.
This explains the roll behaviour, but how does ...
- 13.7k
27
votes
Accepted
Plane that always flies into the wind?
The short answer is no.
All the glider feels is its flight relative to the air. What the ground is doing beneath it is not relevant, the wind could be blowing a hundred kilometers an hour and the ...
- 7,092
25
votes
What does it mean when an aircraft is statically stable but dynamically unstable?
Static stability means that a deviation from a trimmed state produces forces which return the system to this trimmed state.
If these forces produce an overshoot which increases over time, such that ...
- 236k
25
votes
Accepted
Which Provides a Faster Turn - A Horizontal Turn or a Vertical Loop?
Bottom line: you need to keep the aircraft as close as possible to its "Corner Velocity", which is the highest point on its energy maneuverability diagram. (Note, all this comes from an ...
- 6,154
24
votes
Accepted
Can a barrel roll really be executed at a constant 1G?
You are absolutely right, a load factor of greater than 1 is impossible to avoid in a proper barrel roll. The barrel part of its name comes from the spiral path the aircraft needs to perform in order ...
- 236k
24
votes
Can gliding your plane save fuel?
This approach of using an engine is called pulse and glide. It generally works because each engine has an optimal power setting at which it converts fuel into power most efficiently.
If the most ...
- 12.2k
23
votes
Can an encapsulated airfoil generate enough lift to lift the capsule?
Consider Newton’s third law - for any action there is an equal and opposite reaction. If the action is to lift the enclosure then what is the reaction? It has to be pushing against something. You ...
- 1,882
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 ...
- 20.9k
22
votes
Does lift equal weight in a climb?
In an aircraft that is climbing at a constant vertical velocity, the total of the upward-directed vertical forces is the same as the total of the downward-directed vertical forces.
Were it not so, ...
- 11.1k
22
votes
Can we see evidence of "crabbing" when viewing contrails?
Yes, you can see evidence, but it isn't the angular misalignment you are picturing...
The aircraft does not crab relative to the airmass, it crabs relative to the earth. So, you will never see the ...
22
votes
What happens when a helicopter loses the engine and autorotation is not initiated?
If you don't lower collective, the blades slow down and stall and the machine becomes a falling rock, with the rotor eventually slowing to a stop if there is enough time to ground contact. Yaw will ...
- 134k
21
votes
Can hang glider hover straight into wind and keep same position?
The ground is not flat, and indeed slightly angled. This is enough to "hover".
Specifically, the ground slope should be equal or more than the max L/D ratio of the hang glider at the current ...
- 13.7k
21
votes
Why does a sudden tailwind/headwind change IAS?
Why that happens is due to the aircraft's inertia.
Consider a fairly simple case: an aircraft is flying due north, straight & level, with a constant 100 knots of indicated airspeed (KIAS) and a 10 ...
- 52.6k
20
votes
Do airliners reduce their angle of attack to maintain lift = weight as fuel burns off during cruise?
It's almost always more economical to fly higher if you can. So, as an airliner burns off its fuel load, it will naturally want to climb higher, and the pilot will request clearance to do so in stages ...
- 22.1k
20
votes
Terminology: is the "normal acceleration" (nz) considered to be 1 G, or 0, when an aircraft is at rest on the ground with fuselage horizontal?
At zero G, you're floating (Vomit Comet ride). At 1 G, you have normal weight. At 2 G's, you seem to weigh twice as much as usual (60 degree banked turn).
The normal aviation convention is that 1 G is ...
- 52.6k
19
votes
How can an aircraft turn if the horizontal force component is zero?
It is easier if we look only at the forces experienced by the aircraft, and in an inertial frame of reference
In this revised diagram, the vertical component of the lift balances the weight, which is ...
- 301
19
votes
Accepted
What does it mean when an aircraft is statically stable but dynamically unstable?
If an aircraft is statically stable, it will always return to equilibrium after a disturbance. But what happens after can either show instability or stability. This is where the dynamic stability ...
- 1,963
18
votes
Can we see evidence of "crabbing" when viewing contrails?
Crabbing is the misalignment of the aircraft's longitudinal axis with the direction of travel over ground, caused by crosswind.
The crabbing cannot be seen by looking at the angle at which the ...
- 83.8k
17
votes
Can a plane bank without turning?
Yes, it's entirely possible. You can use the rudder to oppose the turn induced by the roll, and thus fly straight. However, doing so means that your nose is pointed off at an angle from your direction ...
- 12.8k
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