engine failure, no flaps??

[747-400]

having been taught circuits with flaps, and with no flaps in the grob tutor (grob 115-E)as well as circuits with a simulated engine failure.
What would happen if flaps could not be operated e.g due to a malfuction, and with an engine failure at the same time.
would it be diffcult to land or is there a set procedure, how would airspeed be controled and there is a increased risk of stalling due to no flaps???????


747-400

[Tinstaafl]

A stall occurs as a result of the wing exceeding a certain 'critical angle of attack'. This will occur at a particular speed that varies according to configuration eg flaps extended or not, weight etc

As long as the aircraft is operated at an airspeed appropriate to gliding in its current configuration ie no flaps, there is no greater likelyhood of stalling than with flap. This airspeed corresponds to a lower angle of attack than the critical angle of attack - so no stall.

The best glide range for a given height will occur at the airspeed for the current weight that corresponds to the best Lift/Drag ratio. This 'Best L/D' ratio is when the required amount of lift is obtained for the least cost in drag.

The more drag there is ie the worse the L/D ratio, the more height must be lost to maintain the current speed, leading to a shorter glide range for any given starting height.

The speed can be controlled to ensure it is maintained at whatever correspends to the best L/D ratio by adjusting the a/c attitude. For example, using an a/c already flying at the best L/D speed, if the nose is raised a little the a/c will reduce speed leading to an increased cost of drag for the lift being produced ==> worse L/D ratio ==> reduced glide range.

The problem now comes down to how to control the glide to ensure the potential glide range meets the ground at the same point as the runway! This is a form of 'energy management' ie controlling the inevitable loss of total energy stored by the aircraft in the form of height & speed.

If the speed is kept constant then it simplifies matters by reducing the problem to a single perceived variable - height - and makes it easier to observe changes.

Energy can be dissipated but is bloody near impossible to regain once lost. It is easy to transfer one into the other & back again

General principles:

Fly the a/c at the best L/D speed.

Make the aiming point on the runway approx. 1/4 to 1/3 along it to provide a buffer for a possible undershoot.

It's better to overshoot, land long & then roll at low speed through the fence at the far end of the runway, than to undershoot & fly through the fence at the near end of the runway.

A slight overshoot (or excess height, if you prefer) is better than an undershoot since it's easier to do something to adversely effect the glide range/lose height than it is to increase the glide range/gain height.

Some ways of adjusting an overshoot are:

1. Turn away from the aim point slightly. This has the effect of increasing the total distance flown ==> more time to reach the runway ==> more height lost since the rate of descent is maintained.

2. 'S' Turns. Same effect as 1. above.

3. Sideslip. Adds drag which reduces the L/D ratio, reducing the glide range. Another way of looking at it is that to maintain a same speed in the sideslip you will have to lower the nose, increasing the rate of descent ==> steeper glide angle.

4. Alter speed away from that for best L/D

If an undershoot occurs then you can do something about it by stopping what you're doing in items 1 to 4 above. If you've used an aim point along the runway instead of at the threshold then you also have the option of using that part of the runway that lies in the undershoot area.

As last resort, accept the approach isn't working & choose to land under control away from the intended runway rather than crash out of control prior to reaching it!!!!!

Turn base earlier than usual. Point directly at the threshold until an overshoot to the aim point can be seen. If you keep the airspeed constant, an overshoot can be recognised by the aim point moving DOWN the windscreen. If the aim point moves UP the windscreen then consider using the threshold as an alternative aim point. If that still produces an undershoot choose another landing site!

As the overshoot develops, turn away from the threshold to fly a more normal base/final pattern. Not so much as to cause an undershoot though. The aim is for a very slight overshoot to be occuring.

Use sideslip to control the remainder of the overshoot.

Once you are certain that you will at least reach the threshold you could consider using more sideslip make your touchdown point prior to the original, inset aim point.

[747-400]

thanks for the info Tinstaafl, sounds very simular to glider circuits


[This message has been edited by 747-400 (edited 12 May 2001).]

[Lucifer]

You'd have to watch not floating into the overshoot in the Grob, due to the good gliding ability without flaps.

[I. M. Esperto]

We practiced no-flap landings in the Simulator, and had to demonstrate one to the FAA for the ATP rating.

Floating is a real problem, but the landings themselves are super-smooth.

Nothing like a long runway into the wind.

Engine out should not pose any real difficulties. If you lose an outboard, set target EPR on the other outboard, and use the inboards for power adjustments.

[747-400]

thanks for the replys, much Appreciated.