Re: Continental 727 nearly belly-flops at O'Hare

From:         Mark Rogers <mmr47784@uxa.cso.uiuc.edu>
Date:         13 Jan 94 05:07:24 PST
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In sci.aeronautics.airliners you write:

>In article <airliners.1993.812@ohare.Chicago.COM> mmr47784@uxa.cso.uiuc.edu (Mark Rogers        ) writes:
>>Normal airline procedure is to respond to the GPWS, THEN determine what
>>caused it.  

>I've never heard of this as a procedure.  The only system which really 
>requires "blind faith" responses (courtesy FAA/company policies) is TCAS.  
>GPWS is notoriously unreliable, and warnings can be rather vague (whoop whoop 
>pull up for four of the five modes, in older systems).  Therefore, the normal 
>response to this *caution* is to reconcile the warning with one's situational 
>awareness.

I was unclear in my orignal post.  If memory from Ground School serves, a 
GPWS warning in IMC does require immediate action.  The last 727 Captain 
I talked to said it is firewall thrust, and +15 pitch.  As the Cont. crew
was in VMC, this would not have been necessary.  With that said, however,
the point still remains that the condition of the gear should have been 
immediately confirmed - There just aren't that many things that would set
off the GPWS.  A check such as: Runway in Sight, normal glide path, gear 
down, landing flaps confirmed would have been sufficient, and prudent.


>I'd probably have ignored the GPWS too, if I was obviously on glide slope and 
>had the runway in sight.  Three sets of eyes ignoring three bright green 
>lights on the gear indicator is a bit harder to rationalize. :-) Warning or 
>not, what happened was *not* a consequence of GPWS being disabled or ignored, 
>but rather the broader airmanship issues of the approach.  

Agreed.  But giving the GPWS the proper consideration would have broken a 
link in the "error chain", and eliminated this incident from discussion.
That's what the GPWS is supposed to do: alert the crew that something in
their situational awareness may not be right, and to reevaluate the conditions.


>>From what I have read, this was one of the flight crews big mistakes- The
>>flaps were left at 25 to keep the speed UP.  Flaps 25 is not a legal landing
>>flaps setting in the 727- that's why they didn't get a horn.  If they had
>>extended the flaps to 30 (a legal setting), they would have heard an 
>>unsilencable horn as the flaps passed through something like 27.5 degrees.
>>In any event, the crew was violating regs if they were trying to land with
>>Flaps 25.  

>I am not convinced of that.  The 727 is certified for flaps-up landings, even
>though there are no charts for that as part of normal ops manuals: the only 
>thing missing at flaps 25 is that they wouldn't have the performance info 
>(well, maybe--it might be in a PDCS, if installed).  Let's classify this as 
>a "gray area."  Perhaps the crew felt they could safely land the airplane 
>on the 10000' dry runway available to them.  Given the ATC constraints, 
>FAR 91.3!

This I find strange.  I believe the 727 is "certified" for flaps 30 and 
flaps 40 landings (thus the heavy black line indicating that all weights at
flaps 25 are above maximum structural landing weight - page L-3).  The 
aircraft can also be landed flaps up- this is, however, an irregular 
procedure, and the checklist involves dumping fuel and observing the max
tire speed if possible.  I don't believe this is "certified", in the sense
that it is acceptable to perform this type of landing on the line.  We would
all agree that an ATC speed restriction should not be the cause of an Irregular
Procedure.  I would also assume (although I'm not sure on this point), that
part 121 would not permit an airliner to land under a configuration for which
performance data could not be obtained.




>---
>Robert Dorsett
>rdd@cactus.org
>...cs.utexas.edu!cactus.org!rdd


--Mark

Oh, by the way, I meant to post this, but I hit the wrong key originally-
maybe you could help out.   Thanks :)