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TOM stall?

Old 21st May 2008, 20:48
  #81 (permalink)  
 
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What happened to the posts pointing out WHY an aeroplane stalls? To strong for here?

SSD
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Old 21st May 2008, 21:46
  #82 (permalink)  
 
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I recently had the opportunity during a flight test program to actually stall a 400...not an approach to stall but rather a full fledged stall. With a weight of about 95000lbs, we were well under 90 kts when we experienced the buffet etc and the aircraft was fully controllable...just kind of mushy. Provided me with great confidence in the 737, as you have to have a serious lapse of brain matter to get yourself in this situation unintentionally.
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Old 21st May 2008, 21:47
  #83 (permalink)  
Per Ardua ad Astraeus
 
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I assume that the reason the posts were removed is that whether or not a 'stall' took place is really irrelevant to the incident. Either the reported attitude or speed alone would make this a serious event and one which would be difficult to control.

I am also sure that a thread in Tech Log or Questions on stall 'definitions' would be acceptable.
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Old 21st May 2008, 22:05
  #84 (permalink)  
 
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Fair points BOAC. I am just a tad concerned that some 'professional' pilots don't seem to know why an aeroplane stalls. I find that a tad worrying.

SSD
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Old 21st May 2008, 22:49
  #85 (permalink)  
 
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More to the point, what qualifies these so called "professional" pilots to comment with any authority or integrity, when, on the strength of various comments on this thread.....there doesn't appear to be any grasp of even the most basic concept of aerodynamics 101.
Instead, comments are made and judgements/thoughts are introduced into a thread..that show little in the way of understanding and show a remarkable resemblence to tabloid headlines.
Or am I turning into a grumpy old man?
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Old 21st May 2008, 23:23
  #86 (permalink)  
 
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Altflaps:

You can be damn sure that there are no other professional groups that regularly accuse each other of all sorts of negligance on a public bulletin board.
Oh, really?

Ahem:

http://www.biofind.com/Rumor/

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Old 24th May 2008, 12:43
  #87 (permalink)  
 
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Just out of interest, what would happen in this scenario?

The aircraft is following a CDA with DA set on in the ALT SEL window. G/S capture occurs, but for whatever reason, the Missed Approach Altitude isn't dialled in?

A G/A is required and perfomred with the A/T and A/P engaged. At 1000ft, FLCH or V/S is selected. Would the throttles start to retard?
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Old 24th May 2008, 14:08
  #88 (permalink)  
 
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Total Beginner,

If you engage LVL CHANGE the plane climbs at whatever speed you have dialled in the window on the MCP.

If you engage V/S the plane climbs at the rate of V/S you have selected. If you have selected say 1000ft/min rate of climb and 240kts, the aircraft will climb at 1000ft/min.

The speed of the aircraft is then dependant upon how much thrust is available at that rate of climb. In a 737 a 1000ft/min rate of climb at 240 kts (low altitude) is easily acheivable and there will be an excess of thrust available. Therefore, the throttles will retard until the thrust commanded is being delivered to maintain 240kts.

However, if you selected say a 5000ft/min rate of climb at 240kts, there might not be enough thrust available to reach this speed, at this rate of climb. The speed will then bleed off and if left uncorrected the aircraft will stall.

With the AP engaged the stall protection system kicks in (on the NG anyway, never flown the classic) and you will get a mode reversion to LVL CHANGE
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Old 24th May 2008, 14:56
  #89 (permalink)  
 
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I think he wants to know what would happen if you hit toga with the mcp alt window set to DA and not MAA. Therefore a lower alt than you are already at.
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Old 24th May 2008, 15:23
  #90 (permalink)  
 
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You do not set DA in the MCP window for a start! Why would you? When you hit Level change or FLCH, the aeroplane will climb with GA power at whatever speed is selected (or current speed at switch selection) until it eventually captures selected MCP altitude. If the MCP selected altitude is already below you, it will continue climbing because it cannot think of anything else to do!
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Old 24th May 2008, 16:06
  #91 (permalink)  
 
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I think he wants to know what would happen if you hit toga with the mcp alt window set to DA and not MAA. Therefore a lower alt than you are already at.
Yes, that was my question


You do not set DA in the MCP window for a start! Why would you?
Maybe not DA, but it might be necessary to set an altitude below platform ALT during a CDA if you are intercepting the G/S from above (not advisable I know).
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Old 24th May 2008, 16:19
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There's nothing wrong with intercepting the GS from above- I did it only today! I don't understand the enormous horror it has for some people. It's something we are going to have to get more used to with CDAs and noise-saving approaches. Once you are cleared for the ILS, all that then matters is you capture the GS before you reach the MCP selected altitude, so be sure to wind it right out of the way or you will find yourself level in seconds and unable to continue the approach. So if you then forget to reset the MCP altitude to GA altitude, and then GA, you will capture that selected altitude, so you must remember to set proper GA altitude after you have captured the GS. There are other complications, for instance, whatever speed you are doing at altitude capture will become then become the captured speed at that altitude. So one must stay well on top of the automatics or disengage them totally (not recommended!). Clear?
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Old 24th May 2008, 16:27
  #93 (permalink)  
 
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So one must stay well on top of the automatics or disengage them totally (not recommended!). Clear?
Notso, on the 737 during a single autopilot approach, if you press TOGA, the autopilot disengages, so you HAVE to hand fly the missed approach.

PP
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Old 24th May 2008, 16:27
  #94 (permalink)  
 
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so be sure to wind it right out of the way or you will find yourself level in seconds and unable to continue the approach.
This is what I mean. If you wind the MCP ALT down to something like 700' so that you can continue in V/S, but then forget to set MAA after G/S capture, what happens when you select FLCH to begin the cleanup if you've already passed this altitude in the climb or initated the G/A from above it? Is there a built in safety feature whereby having G/A as the target thrust means that FLCH will ONLY command a climb, or will the aircraft go into: IDLE | HDG | FLCH SPD because the selected altitude is below you?

Last edited by TotalBeginner; 24th May 2008 at 16:50.
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Old 24th May 2008, 17:32
  #95 (permalink)  
 
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and can we put this one to rest:
BTW I knew a Flight Engineer on Concorde; he reckoned he & his colleagues tried to recreate the Sioux City recovery in a Sim, and anyone who got within 40 miles was doing very well ! Respect indeed ! You may be able to corroborate that.
By accident or design (usually this), simulators I have handled have borne little resemblance to the real aeroplane in all respects, always most seriously on the adverse side of the real aeroplane. Without denigrating the achievement of that crew in putting the Sioux City aeroplane down on the airfield, a better representation of the event created in the simulator would be more illuminating. Simply...simulators suck. They bear little resemblance to reality. So the above statement is actually doing down all other pilots.

They were just an ordinary crew on the day who were called upon to achieve something sensational, and they preformed superbly. There is no need to do down the rest of the aviation community to talk them up! And they would not have wanted that either!
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Old 25th May 2008, 07:05
  #96 (permalink)  
 
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If it helps.....on the 757/767.......if you have the MCP alt set at a level below your present alt and then hit TOGA you will get a pitch-up to a GA with a 2000fpm climb (or full, which ever is less) until it hits the target alt [ which it will never manage to do in this case]
Think about Palma for runway 06L where the GA alt is 2000 but the approach round the corner is going to be in the region of 2500. If you GA early it will pitch up as the first part of the GA and then climb to FL400-ish unless you stop it.
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Old 26th May 2008, 21:11
  #97 (permalink)  
 
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Simply...simulators suck. They bear little resemblance to reality.
I'd say, more correctly, sims work well within the normal operating environment of the aircraft they represent - that's the spec they're programmed to, and the programmed 'model' is unlikely to be accuarate much beyond that spec (why would the manaufacturer waste money making it so?).

Step outside that envelope, and you are almost certainly outside the mathematical 'model' within the sim's computer. The results will be unpredictable, and almost certainly not what the real aircraft would do (the further away from the 'model' you are, the more likely this is).

SSD
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Old 26th May 2008, 21:36
  #98 (permalink)  
 
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I am guilty of not having read all postings on this thread.

But since the 'event' occurred in November 2007 and still no report from AAIB, doesn't that suggest the whole thing is nonsense?
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Old 26th May 2008, 22:08
  #99 (permalink)  
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doesn't that suggest the whole thing is nonsense?
Not quite sure what you mean by this. If you mean nonsense as in 'never happened' then, no. It happened and was close enough to coming unstuck for the AAIB to treat it as an accident.
 
Old 26th May 2008, 22:15
  #100 (permalink)  
koi
 
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Yes...it happened
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