This is what happens.....

[Deadstick]

When it's high, hot, humid and heavy and you decide to try to fool mother nature.

http://www.youtube.com/watch?v=QT29xWWWqZU

[guamainiac]

Just after solo I came very close to that. Plane had been "topped" the night before and the heat the next day skyrocketed.

The straw ... a small hill formation a few miles off the runway provided just a trickle of negative lift first arresting climb at 100 feet and then putting us into sink.

Doing a slow shallow turn away from the source of sink provided distance but watching the squirrel nests and commenting on how much cement was caked on a few trucks in the concrete yard or noting how easy it was to tell between the cinder or the concrete block piles passed the (terror filled), moments. Not true terror but a period of exceptional concern, with the "180" complete and the vario "not doing anything" ... sometimes not doing something is good.

Ego and disdain played a part of this. A bit of mine for sure, wanting to prove myself, and the massive ego of one one of our lead instructors who had it in for a much better person I signed on with (Check captain for a major line as well as and AF instructor). Still, I should have been looking at the details.

[Gabriel]

http://airdisaster.info/forums/viewt...p=59158#p59157

[3WE]

Great post Guramaniac....

My personal reaction to this has been interesting....

"Yeah, what a total dumb-turd, how in the world could he do that 3 mile takeoff run and continue, didn't he know he was hot, high and heavy?"

Nope, it's not that simple...(remember, he was a good, experienced pilot- and, of course lots of people that crash are good and experienced).

I have never flown "high"...but who isn't a decent pilot and noted what climb out is like when you are light on a cold winter day and heavy on a hot summer day...The atmosphere and your load affects performance on EVERY takeoff......

I would bet a beer that the pilot said to himself, "wow, I'm kind of hot, high and heavy....." Probably more than once on that takeoff.

But the other thing he said to himself was- The plane always takes off- and I HAVE done hot, high, heavy takeoffs before....again, the plane always takes off....

I am accelerating....I am taking flight....When I ditch the drag of the grass, I will climb......Planes have power not just to fly but to climb and to turn....I can climb away.....I always do....

This film has been a teachable moment....it's not that he said "to hell with my performance parameters".....it's that light plane guys do not have (OMG- I'm about to say something scary)....they do not have a "black and white" decision tree.

The guy failed on not having two decision trees: 1) Should I go flying or not (with this load) and 2) At what point do I call off the takeoff and stop- yes there were opportunities and sitting in my arm chair- I see ALL The warning signs! DUDE...stop...you have nice smooth grass and plenty of room and you STILL aren't flying.....no, not the trees, not the rising terrain....

OUCH- if he had just had those decision trees- the plane and his upper lip would be in much better shape.

But good ole tunnel vision....the plane has ALWAYS taken off- even after doing many hot, high and heavy departures- yeah, the takeoff run is long and the climb is anemic- but I ALWAYS...ALWAYS clear those trees...

[Deadstick]

Originally Posted by Gabriel

http://airdisaster.info/forums/viewt...p=59158#p59157

Great post Gabriel. Exactly what I was thinking.

[UncleFire]

Maybe a dumb question, but that plane has flaps right?

Look at the video from 2nd camera in the back. What I'm thinking are flaps are not set.

[3WE]

Originally Posted by UncleFire

Maybe a dumb question, but that plane has flaps right?

Look at the video from 2nd camera in the back. What I'm thinking are flaps are not set.

Correct.

General, fundamental rule: [do not read Evan]

With light planes, flaps generally only reduce the ground run while reducing climb performance (because they generate additional, overall drag). (Actually, I'm not sure if big planes don't want to ditch flaps ASAP if they had a climb challenge)

Evan, consult the POH for that aircraft, weight, altitude and temperature report back what it says regarding flap use.

[3WE]

...speaking of general, fundamental rules:

'Never' take your hand off the throttle in critical flight phases.

He did that right.

[Gabriel]

And more importantly:
No matter what, never stall spin crash burn die.
He did that right too. I feel many pilots would have fallen in the trap of trying to squeeze from the plane a performance that just was not there, and would have stalled and likely spun.

[Peter_K]

Originally Posted by 3WE

, (Actually, I'm not sure if big planes don't want to ditch flaps ASAP if they had a climb challenge)

One of the basic rules of Airmanship is do not retreat flaps before a positive rate of climb is established. If you do, the aircraft will most definitely sink.

[Gabriel]

Originally Posted by Peter_K

One of the basic rules of Airmanship is do not retreat flaps before a positive rate of climb is established. If you do, the aircraft will most definitely sink.

Sooooo....

If the airplane has not yet established a postive rate of climb.... and you retract the flaps... the plane would most definitely sink... from where?

[Peter_K]

Originally Posted by Gabriel

Sooooo....

from where?

Somewhere above the wing ground effect.

[Gabriel]

I know, I know. It was a sort of joke. I just thought of this "advise":

"If the plane can't start to climb, don't raise the flaps or it'll descend"

And I couldn't but laugh.

That said, and in a more serious note, and don't try this at home, but if I was flying the Tomahawk and I was in the same situation of this accident, with the plane unable to climb out of ground effect, and I was already at Vy, and I had one notch of flaps put, I would definitely retract the flaps.

Vy with one notch of flaps is a tad more than 20 knots above the clean stall speed, so while the plane would initially tend to descent if you just raise the flaps without taking that into account, you can easily avoid that by pulling up just a bit first (trading a bit of speed for a climb rate for a second) and then retracting the flaps.

I'd almost assure that that reduction in parasitic drag will give you the extra performance needed for a sustainable climb.

Disclaimer1: The best way out of this is never get into this. Consult your take-off performance charts.
Disclaimer2: While I am pretty used to the behaviour of the flaps in the Tomahawk (a lot of drag, minimal effect on stall speed) and I fell confident of the explanation above, nowhere the manufacturer recommends that nor have I ever tried it.
Disclaimer 3: Other planes can have notably different flap behaviour, so even if the above applied to the Tomahawk, it means nothing for other types.
Disclaimer4: In general, when taking off with flaps, it is supposed that you already know that the plane WILL climb out without problem (see disclaimer 1), and it is a very good idea to wait, before raising the flaps, until the plane is stabilized in a climb (i.e. climbing at constant airspeed and climb rate), at an airspeed safe to continue with the flaps up, and at at least some minimum altitude as to be able to correct any initial tendency to sink.

[3WE]

Originally Posted by Peter_K

One of the basic rules of Airmanship is do not retreat flaps before a positive rate of climb is established. If you do, the aircraft will most definitely sink.

But the real question is unanswered- do airliner flaps generally degrade climb performance, and should the be retracted for the best climb performance?

Yes, you would not mindlessly retract the flaps while barely lifting off/mushing in ground effect in an airliner.

Of course, neither would you be making a takeoff run in an airliner with weight and weather that makes for a negligible climb ability...(at least I hope not).

I'm sure Gabriel can answer- I could see a small envelope where flaps give you more lift with 'less' relative drag- but in general, flaps are usually generating a lot of drag.

My money is on the procedure for the best rate of climb being to take off, get a healthy airspeed and a reasonable safety-buffer of altitude and then bring up the flaps!

...and in a small plane, leave them up for the best climb performance. (It would take a very special situation where the ground is mushy- and generating drag- so that it would be better to take off with flaps, and then retract them in ground effect (with critical attention to all controls, airspeed, attitude,) and then climb out.

[Gabriel]

Originally Posted by 3WE

But the real question is unanswered- do airliner flaps generally degrade climb performance, and should the be retracted for the best climb performance?

Yes, you would not mindlessly retract the flaps while barely lifting off/mushing in ground effect in an airliner.

Of course, neither would you be making a takeoff run in an airliner with weight and weather that makes for a negligible climb ability...(at least I hope not).

I'm sure Gabriel can answer- I could see a small envelope where flaps give you more lift with 'less' relative drag- but in general, flaps are usually generating a lot of drag.

My money is on the procedure for the best rate of climb being to take off, get a healthy airspeed and a reasonable safety-buffer of altitude and then bring up the flaps!

In general, but not always, any amount of flaps or slats in any condition adds drag. Parasitic drag is the obvious factor here, but typically also induced drag is increased. It's a bit tough to explain, but the most efficient way to produce lift is to push down the air with the same downwash all along the wingspan. Pushing down "half of the air" with less downwash and the other half with more downwash might produce the same lift (than all the air with the same downwash), but will necessarily take more energy to do, and hence more induced drag.

The exception is below some threshold at very slow speeds. Because of the flow separation, the parasitic drag skyrockets as the plane nears, reach and exceeds the stall AoA. Thus, if at a given slow speed you are somehow far from stall with a given flaps/slats setting but would be close to stall or stalled without flaps/slats, then probably the "clean" configuration will be more draggy and inefficient (in fact, "stalled" is not only inefficient but unsustainable).

In planes like the Tomahawk, where the stall speed is nearly the same with or without flaps, the above is not an issue.

In transport jets, with full span slats and maybe 70% span multi-slotted Fowler flaps, the difference in stall speed can be quite substantial (especially between the clean config and a take-off-ish config, once the slats are extended and the flaps are at say 15°, further extending the flaps add a lot of drag and little lift).

Hence, the issue here to retract the flaps is not as much achieving a positive rate of climb and some altitude, but attaining some speed where you will still be with a margin above the stall speed once the flaps are retracted to the next notch.

The usual take-off / climb schedule is:
Rotation
Lift off happens at a speed with a margin above stall
Positive climb - gear up
The plane keeps accelerating and pitching up until stabilizing at V2 +10 / +20 and a pitch of some 15 / 20°
The plane could keep climbing like this almost forever (okay, you typically have a 5 minutes limit for TOGA thrust), but it's not efficient and it makes a lot of noise (both the engines at TOGA and aerodynamic noise of the "dirty" plane), so "as soon as possible" (*) the idea is to level off (or substantially lower the nose and reduce the climb rate), reduce thrust to "climb" setting, accelerate, and start retracting the flaps and slats in increments as the increasing speed allows (this is called flaps retraction schedule) and keep accelerating to the optimum climb speed or 250kts (whichever is lower) and then pull up again to keep all the excess thrust (that so far was being used to increase airspeed) in climb.

(*) As soon as possible:
- Typically the reduction in pitch and thrust and the flaps retraction schedule is not done below 1000 or 1500 ft AGL. There are several reasons for this: First, while in the end cleaning up the plane will mean a more efficient climb, the initial reaction when you lower the nose to accelerate is to worsen the climb (in favour of speed). You want to gain a "healthy altitude" quickly before any level-off, so as to have margin to manage a situation like an engine failure, a windshear, etc. Also, to avoid workload saturation, it is good to give a little of time to the pilots to stabilize in the initial climb and check that all is Ok before proceeding with the next sequence of tasks. Remember, it will take just 20 to 30 seconds to reach 1000 to 1500 ft.
- Compare this two situations: a- You are in take-off config climbing 3000 fpm with TOGA at 170 kts. b- You are clean, climbing 3500 fpm with climb thrust at 250 kts. Clearly, "b" is a much more efficient climb: you are climbing more feet each minute, making more miles each hour, and burning less fuel. Yet, "a" has a much steeper climb gradient (you are climbing more feet per mile): 3000/170 is quite more than 3500/250. Also,a s said before, before climbing "better" (after cleaning) you first have to climb "worse" (level off for the flaps retraction schedule). Because of these two factors, terrain and obstacle clearance my require to delay the level-off and flaps retraction.
- Sound abatement: While climbing clean and at climb thrust is much more quiet than doing so at TOGA and "dirty", depending on some factors sound abatement procedures might call for the level-off, thrust reduction and flaps retraction to be done LATER (say at 3000ft). Imagine the normal profile: The plane climbs at TOGA to 1000ft, levels off, accelerates and retract flaps and slats, keeps accelerating to 250 kts. Pause. Let's call this point above the ground "point X". After point X the plane will resume climbing with climb thrust and 250 kts. Now imagine the "sound abatement profile". The plane climbs at TOGA, up to 1000ft both profiles are equal, but in this case the plane keeps climbing to 3000ft, and only then levels off, reduces thrust and starts the flaps retraction schedule. When the plane overflies the "point X" of the normal profile, it will be at 3000ft instead of 1000. Maybe making more noise (if the flaps retraction schedule is not yet completed), but the noise received on ground is proportional the the amount of noise generated and inversely proportional to the square of the distance, so being 3 times higher the noise on the ground will be 1/9 (if the intensity of the noise generated was the same, but in any event the intensity of the source it will not be 9 times louder).

If performance was the only concern you would level off and retract flaps / slats ASAP (or you would take-off clean if you could). But it is not.

[brianw999]

I am but an 18hr lapsed student pilot (and many years lapsed at that) but there's one factor in the above excellent arguments that I couldn't give a shit about and I'm speaking of noise.
If staying airborne means that the NIMBY's below have to put up with a bunch more noise then so be it.

It will still be quieter than the sound of me hitting their rooftops !!

(for the uninitiated, NIMBY = Not In My Back Yarder.... A.K.A. the people who moved to live next door to an airport long after the airport was opened......and then complain about the noise !!)

[3WE]

Originally Posted by Gabriel

Clearly, "b" is a much more efficient climb: you are climbing more feet each minute, making more miles each hour, and burning less fuel. Yet, "a" has a much steeper climb gradient.

...I seem to recall that you pointed out that:

When you are in a situation of negligible climb perforance, there is 'no difference' between angle of climb and rate of climb. (zero feet per minute = zero feet per mile, even though the units don't match)

In other words, your flap condition is more draggy and the plane isn't going to climb at all but descend, but if you are clean, then you can maintain altitude/eek out your miniscule climb rate.

[Gabriel]

Originally Posted by brianw999

... there's one factor in the above excellent arguments that I couldn't give a shit about and I'm speaking of noise.
If staying airborne means that the NIMBY's below have to put up with a bunch more noise then so be it.

Of course. The noise abatement procedures don't apply in an emergency, and even if they did, in an emergency the captain has the legal authority to deviate from any regulation he/she deems necessary to cope with the situation.

[Gabriel]

Originally Posted by 3WE

...I seem to recall that you pointed out that:

When you are in a situation of negligible climb perforance, there is 'no difference' between angle of climb and rate of climb. (zero feet per minute = zero feet per mile, even though the units don't match)

That's correct. Vx and Vy converge to each other as you approach the ceiling.

In other words, your flap condition is more draggy and the plane isn't going to climb at all but descend, but if you are clean, then you can maintain altitude/eek out your miniscule climb rate.

That's correct (with the previously explained exception that if you are at a speed that retracting the flaps would put you very close to the stall, you might get more drag without flaps than with them).

The typical take-off and climb sequence was for normal situations. Not emergencies.

Remember, unlike GA flights, commercial flights have to be "dispatched", and that includes making all the take-off weight calculations to ensure, among other things, that if the most critical engine was to fail at V1, you'd still be able to take-off and achieve V2 and 35ft on the remaining runway, and then achieve a certain minimum positive climb gradient (with a margin, since the regulations mandate to degrade the demonstrated performance).

That is why it's very unlikely that you see an incident like this one in a commercial jet flight.

That said... I'm not sure I'd want to know the outcome if these planes had lost an engine shortly past V1:

http://www.youtube.com/watch?v=ThoZNxy2JZk
http://www.youtube.com/watch?v=ovWmI...eature=related
http://www.youtube.com/watch?v=21qZP...eature=related

(anyway, these planes had more problem with taking off within the runway than with climbing afterwards, so taking-off with less flaps was not an alternative and I don't think that raising them immediately after lift-off would have been a good idea either)

[3WE]

Originally Posted by Gabriel

The typical take-off and climb sequence was for normal situations. Not emergencies.

Still...you are at Las Vegas, in a valley, with a full load of Gamblers and their luggage and a good load of fuel, going to New Yark.

It's 110 degrees, but fortunately LAS is only ~2000 MSL.

The book says takeoff works well.

The book says you will climb and eventually clear the mountains.

But I have rode planes that did 270 degrees of circling on climb out- I assume to get over mountains...

So, you would want to retract the flaps 'as soon as possible' for the best climb performance (I did catch the Vx vs Vy comment- there could be exceptions).

However, one final disclaimer/wiggle word special- The "normal" climb out procedure probably does not delay flap retraction to any huge level of practical significance- climb out costs $$ and flaps are probably ALREADY retracted 'as soon as possible' (ASAP = as soon as REASONABLY possible and not as soon as aerodynamically possible)