Making aircraft stay before landing

[pplaspire]

Hello everyone,

I'm a new bee and a RTR aero license holder. I have a doubt on the capability of making the flight stand still in the air(no hight gain).

Is that possible, becouse I have seen many aircraft stand still near the airport in air for a minute or two or may be longer.

I mean stand still is relative ground speed 0

Please advice details will be of great help.

with friendly regards
aspiring PPL

[EGBKFLYER]

Have not only flown at 0 ground speed but backwards too!

If you have an aircraft with a low enough stall speed and a high enough wind, it's possible. In my case, a Schleicher K8 glider and a 40kt wind...

Why do you want to 'stand still'? You can do that more easily and cheaply on the ground or any time you like in a helicopter...:)

[pplaspire]

Hi ,

Thanks for the immediate responce.

It is actually a technical question.
If a passenger aircraft or cargo aircraft that is approaching an airport and needs to land but doesn't has yet the right thing and must wait for a while.

THere are two things that you can do
1. Rounding around the airport
2. if the waiting time is in minutes can stand still.

and I have seen near the airport sometimes the flight seems to be standing(still). Is that theoritically possible ? and is that practised anywhere ?
or was a mirage that I couldn't see whether the flight was moving slowly.

Thanks in advance

[Piltdown Man]

When you have to "wait" before landing (it's called "Holding"), you normally fly the aircraft at a speed determined by the manufacturer of the aircraft as being a speed where you are relatively fuel efficient. On a Fokker 100 something like 210-220 knots or so (it varies by weight and altitude). On Boeing aircraft that speed would be considerably higher for various other reasons and for a turbo-prop something like 150 knots. At the same time you fly around a pattern that is some called a "Racetrack". Standing still is not a practical option when you are flying although it may appear to be an optical illusion from the ground.

[Tinstaafl]

Very few a/c can 'stand still' as you put it. Helicopters can, blimps & dirigibles can, specially designed a/c such as the Harrier can, and a few odd research platforms eg the 'flying bedstead' of the 1960's (date?). Some particularly powerful military fighter types and high performance aerobatic aircraft can be made to point skywards while having some amount of support from their engine's thrust but that's usually measured in moments, not minutes.

Apart from those sorts of things other a/c need to move forward through the air to generate the lift that keeps them airborne. They all have minimum speeds at which sufficient lift is produced. *IF* they happen to be flying into the prevailing wind *AND* the wind is at least equal in speed to the aircraft's speed then the aircraft would be stationary over the ground. Think of a boat travelling upstream in a fast moving river. If the river's speed is fast enough then eventually the boat will not make headway compared to the shore. It needs to be a very strong wind for an aircraft to make little or no headway.

The options used to delay progress of an aircraft include reducing speed (but there's a limit to how slow any particular aircraft can fly), not flying directly towards the destination - which will delay the eventual arrival time - or to 'hold' by flying circles or racetrack patterns over some area until the need to hold is no longer present.

[barit1]

Understand too that a very large aircraft (widebody) in approach configuration only travels one fuselage length per second.

So if there are no nearby points of reference (or if the reference points are moving the same direction), one gets the illusion of it almost standing still.

You generally won't get this illusion with a smaller aircraft.

About flying into a headwind: Aircraft have taken off, climbed (without turning) to the level of max. headwind, slow-flying with a negative groundspeed back across the airport, then descending and landing on the same runway without ever turning. A college roommate of mine did it in a Piper J-3, but I've heard of bigger aircraft doing it too.

[LondonJ]

Say you're in a high performance aerobatic plane with no wind and you are pointing vertically up with just enough power on to maintain height. How do you control the attitude of the plane as I assume 0 airspeed means no airflow over the control surfaces?

[pplaspire]

Hi All,

It is great to have talking to well experienced like you guys. I'm clear now, That it is an illusion seeing an aircraft stand still airborne.

One more theoritical view.

Can a propeller generate such a volume of airflow on the wings so that the lift can be created ( Please treat this as theoritical or ideal situation ).
The propeller that can distribute the airflow through the wings.
Given these situation a boeing 737 can be airborne without moving forward( 0 or negative ground speed and the headon wind is not favourable ).
Well does passenger or cargo airfcrafts possess such theoritical capability but may be becouse of the safety the manufacturer suggest you the other way.

Thanks for all your response

[Farmer 1]

Londonj,

I suspect you are correct in your suspicions. I've seen the manoeuvre done once. As the aircraft's (upward) speed approached zero, torque reaction from the engine took over, and the aircraft began spinning in the opposite direction to the propeller.

Pplaspire,

Are you confusing propellers and jet engines? The wing area behind a propeller is only a small part of the total wing area, so it cannot produce enough lift to allow the aircraft to fly in zero wind. the engines on a Boeing 737 are beneath the wings, and so do not produce any lift.

There are a small number of aircraft designed for short take-off and landing which have the engine exhaust flowing over the upper wing surface. This gives an increase in lift, but not enough for flight in still air.