Why am I stalling ?

[Tomcat61]

Hi all, I have been flying various city to city flights in the FTD 757, and had no problems.
But last night I set up Seattle to Vancouver, and pre take-off, I set my runway heading, I set the Alt to 30,000 like every other flight, and VS to around 2.500 Per Minute, I set Speed to around 275 Knts, Flaps 15.
Ok  I take-off, and l Lift up, and bring gear up, at around 3000ft I retract Flaps, I always do this, and I can leave the room, and come back and my aircraft has reached 30,000 no problems, but with this Seattle to Vancouver, at around 6000 ft, the nose starts to come up, and it keeps going up, to around 45 degree's, then I stall, and I cannot control the aircraft.

Why is this happening all of a sudden, or is it something to do with my Seattle to Vancouver ?

Thanks for any feedback.
Tomcat61

[jaythree]

I have a few obvious questions,
did you actually engage the autopilot and auto throttles?
did you check your fuel state?
is it possible you have a malfunction enabled, even by accident ( it sounds somewhat like an autotirm problem)
is it possible your joystic calibration is off and causing a fight with auto trim?
Try reducing your rate of climb as well.

[ysteinbuch]

I had the same thing happen to me a couple of times. I had to disengage the autopilot and get out of the stall. I noticed that my trim was off, so I reset it and the rest of the flight went fine.

[RollerBall]

As in real life, a/c like the 757 will NOT maintain a 2500 fpm rate of climb at altitude esp with a full fuel load.

You need to begin reducing this in steps. At fl 300 I would think you should be at no more than 1500 fpm, probably less.

That's why it's trying to raise its nose to an impossble angle and stalling out. Even so it shouldn't be happening as low as 6000 ft.

Also in the cruise you should be using mach not ias. At fl 300 you should be going for something like .75 - .78 mach. If you use ias at high alt you are likely to run into overspeed problems.

[codered]

It is possible the aircraft was trying to maintain the 2500 fpm but the airspeed was bleeding off and kept trying to climb to maintain that particular speed?

I would try it again and just make sure your autopilot settings are correct and all else is good.  Fuel is in a proper amount etc....

[Heber98]

I think it would be cool if you could make the autopilot prioritize functions, like NOT holding a VS setting if it means a loss in airspeed when IAS hold is on. I guess it's not possible since the autopilot doesn't control speed by pitch.

[terbert]

I also have stalling problems when under the following conditions, whether they apply to you I do not know, but could be.
1. If autopilot is engaged BEFORE becoming airborne,
2. After landing, it is impossible to take off again and use the autopilot, as in circuits and bumps, unless you click End Flight and start from scratch.
Even if autopilot is disengaged for landing, and you take off straight away, and then engage autopilot, I still stall. so do not despair, we all have problems
regards TC (terbert)

[Hoot]

While nearly every commercial aircraft will pop right off the runway, none can maintain that kind of climb rate. In anything bigger than an RJ85 (BAe-146) you need to keep the climbrate down around 2,000 feet a minute. Why? In a word, thrust. At sea level your engines can and will let you zoom it up to 6k or so, but after that those engines choke for air. Less dense air means less thrust, less lift, and a higher angle of attack on the wings. Eventually the thing will stall out due to a lack of airspeed. The engines can't produce enough power to keep you at 275 knots and climbing at 2,500 ft/min.

Some notes....

1: You can't turn on the autopilot while you're still on the runway. It'll stall out after getting airborne.
2: 2,000 ft/min is too high a climb-rate for nearly every AC. For reference, I've stalled the default 737 at 265 knots with 20 degrees nose up trying to climb too fast. Airliners need more airspeed to avoid a stall than any other plane out there.
3: Set the altitude, NOT the climb-rate-hold, and leave the rest to the computer.
4: By setting the airspeed to 260 knots you probably won't have to touch the throttle once until you begin the approach.


General procedure....
1: Set heading bug for your desired heading after takeoff
2: Set course OBS needle to runway heading
3: Set autopilot for desired speed (less than 250 kts below 10k) and altitude. Do not manually set the VS-hold
4: Set flaps to takeoff norm and takeoff manually
5: Engage autopilot after picking up some speed to avoid a stall and retracting flaps
6: Watch the aircraft until it settles on base course (set with the heading bug)
7: Reset airspeed to 265 knots after passing 10k feet
8: Do not mess with the climb rate unless the aircraft's angle is getting to be too high. The nose will come up to some absurd angle while the speed drops off slowly. If this happens, kill the autopilot and manually get it back under control


Enjoy!
---------------
Hoot

[RollerBall]

3: Set the altitude, NOT the climb-rate-hold, and leave the rest to the computer.

Sorry - you have to adjust climb rate in steps as I mentioned earlier.

The rate of climb is NOT controlled by the computer. It is pre-set by the fde designer and stored in each aircraft's aircraft.cfg file. This is taken from a POSKY 767

[autopilot]
autopilot_available=1
flight_director_available=1
default_vertical_speed=800.000000
autothrottle_available=1
autothrottle_arming_required=1
autothrottle_takeoff_ga=1
autothrottle_max_rpm=97.000000
pitch_takeoff_ga=8.000000
use_no_default_pitch = 1
use_no_default_bank = 1

Note the figure of 800. This is set low so that when you switch to autpilot after takeoff airspeed builds up quickly (..to the 250 you will have preset). Then you adjust it initially to eg 2500 for the first few thou, reducing it in steps as you climb to maintain airspeed in the climb.

As I mentioned earlier, in a heavy flying at altitude, you are advised to check out the cruising mach for your aircraft (usually .75 - . and switch to mach from ias as you're climbing. That's if you want to do it properly!!

;-)

[Brett_Henderson]

I've stalled the default 737 at 265 knots

You may have initiated a looming stall (when pitching up 20 degrees at that speed), but at 265 IAS you're still flying...

[jaythree]

not to step on your toes hoot but

Some notes....

1: You can't turn on the autopilot while you're still on the runway. It'll stall out after getting airborne.

wrong,
you can engage it when ever you want however I suggest that you wait till you are over 100 knots before engaging alt hold, and keep your rate of climb to 1000 ft/min untill you are cleaned up and have some speed.