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Date: Tue, 15 Dec 1998 22:06:22 -0600
From: Snowbird <snbird@ibm.net>
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Subject: Re: emergency decents
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JStricker wrote:

> I base it on the comments of my MEI (25,000 hours of experience), my 
> older brother (also an MEI, CFII, and former FlightSafety Instructor
> with 15,000 hours experience), and the DE that gave me my ME
> checkride, (another 12,000 hours experience).  All threee of them are > in agreement that in an unpressurized aircraft the need for a true, no > holds barred, all out, emergency descent is extremely rare. 

Do you think they might be a little biased by their experience
(ME instructor, Citation pilot owner/maintainer of own planes
rather than flying other people's singles all the time)?

I've heard that smoke in the cockpit is not uncommon with airline
flights; I'd be kind of surprised if there aren't fires and smoke
in singles as well.

Now, whether it's a lot less common than losing pressure in a
pressurized aircraft, I couldn't say, but I'd want to hear some
wider spread of data before I'd conclude it's something a SEL pilot
shouldn't worry about.

I've already had to worry about it once, and I ain't been at
this long.

> In an unpressurized airplane, smoke in the cockpit is one of the 
> very few, and before I did a true emergency descent, it would have 
> to be serious smoke.

It's a judgement call, but if you've ever seen safety training 
films enough fumes to incapacitate a pilot can be produced by
not too much burning synthetic material, and a little flame can
turn into a big fire in a hurry.  Now the good news is aircraft
wiring etc is supposed to just smolder, and not put out toxic
fumes.  The bad news is if the problem is an oil or fuel line
rupture in the cockput, all bets are off.  Also older wire doesn't
meet the same standards and sometimes non-approved materials are
used in repairs.

We had a little smoke, which went away promptly when I killed
the electrics, and no real good choices about where to go
(airports below us socked in).  Kind of Hobson's choice. But if 
they'd been VFR, I would have headed for the ground pronto and
sorted the problem out on the ramp.

> >One doesn't just want to descend, one wants to have the best chance 
> >of keeping the plane under control and of LANDING safely in minimal 
> >distance once descended.
 
> Well, depends on the a/c. 

Any aircraft is going to land more safely and in a shorter distance
if its already going slower as it nears the ground.

> This is the method taught at FlightSafety for Citations.

I don't know about ME planes, but I've heard that jets are a
totally different proposition than light singles wrt how they
handle in slips -- that basically it's not a good idea to slip
them much.

So I wouldn't judge a SE maneuver by that.  What's best for a jet, 
a turboprop etc is not always what's best for a light single, and
probably true of ME planes as well.

> >Speed at the top of the white arc, full flaps (or 20 degrees in a
> >C172), full control deflection slip will IME produce a very similar
> >rate of descent to Vno, while allowing much more margin for error
> >(no concern for overspeeding or overbanking).  And it won't get you
> >to the ground with a large quantity of excess energy which must be
> >expended before the plane will consent to settle down and land.
 
> Try it.  I think you'll be surprised.  

I *have* tried it John.  I can get about the same descent rate
either way, but there's no surprise at the ground level; it's
going to take a heck of a lot longer to land from Vno than from
Vfe.

> Much higher workload than maintaining a 30 degree bank that simply 
> wanted to level itself out. 

30 degree bank that simply wanted to level itself out, ha, ha, ha,
ha.  Yeah, you're right, it depends on the plane.

> Since we are roughly, at 2,000' MSL at ground level, we only have 
> about 8,000' to lose if we start at 10K'.  I prefer not to do this 
> demonstration to the ground :-), so we ended the maneuver at 4,000' 
> MSL.  That leaves 3,000' at Vno.  Roughly 45 seconds, and not really 
> that since you start to come out of the maneuver at least 500' before > your target altitude.  That's where my comment of a few seconds came
> from

That's my point, John, you're only considering the time involved
in altitude loss (and a small altitude loss of only 3000 ft at that).

If you're dealing with a reason to get on the ground quickly,
such as smoke in the cockpit, or a fire, the time involved in
slowing the plane up and putting it on the ground survivably must
also be considered.

Whether a minute and a half to lose 6000 ft is 'a few seconds'
or not I guess is a matter of semantics

Regards,
Snowbird


