[jhb_airlines] Re: Standard Procedure

  • From: Gerry Winskill <gwinsk@xxxxxxx>
  • To: jhb_airlines@xxxxxxxxxxxxx
  • Date: Tue, 25 Oct 2005 14:21:24 +0100

The other factor is that the largest market is the USA. American patriotism, arrogance, or is it insularity, leads them to consider that anything not US designed and manufactured can't be any good. Hence the continued existance of Lycoming, Continental and Harley Davidson.

Gerry Winskill

Bones wrote:

Tandem engines are safer in that they don't produce any yaw on failure (not
much anyway) so you only have to worry about securing the engine. In pure
aerodynamic terms they make much more sense but they aren't popular. Against
them are that two engines bolted to the cabin shell produce much more noise,
rear engine cooling is tricky and rear prop efficiency isn't good (it's
getting disturbed air from the front prop and the body).

Don't start me off on engines again - I still think it criminal that we are
still using Lycoming's antiquated blocks of metal that were designed in the
late 1940's. I'm not sure why aviation is so afraid to see any progress -
maybe the authorities are afraid to move up from a very basic (and safe)
powerplant because they fear additional complexity will result in lower
reliability and more accidents.

I find it absurd that an O-360-A3A in a Cherokee is still burning 10 gallons
an hour as it would have in 1958. No progress, no attempt to improve on all
the wasted unburnt fuel. I'm pretty sure that a modern powerplant could
produce much more output on 10GPH - or could be a lot smaller for the same
power.

Until they replace these antiquated monstrosities GA will remain stagnant.
The engines are expensive and drive up the price of a "serious" design.
That's what caused the growth of the ultralight market and this will
continue to expand (and get better) whilst real GA continues to decline.

The trouble is that Lycoming aren't interested in doing anything but
overhauling thousands and thousands of used units and building a few new
ones. Maybe they laid off their design staff back in 1977 after they
stretched the O-360-A3A into the TSIO-540-C4B5 of the PA31. <g>

bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 25 October 2005 08:58
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Standard Procedure


So, are the few surviving push pull types intrinsically more safe?

The CAA, apart from ongoing efforts to kill off GA by legislation, seem
to take no worthwhile action to eliminate one major killer; car icing. When
they've identified its disaster potential so often, how can they
continue to certify any carburetter equipped GA engines. For new a/c I
would have thought fuel injection would, by now, be mandatory.

Gerry Winskill

Bones wrote:



The bank should be applied to all engine failure cases as it is related
to the adverse yaw caused by the failed engine. The critical engine
isn't relevant here - but it is highly relevant in the case of pilot
limitation. If the critical engine has failed then the yaw is greater
(and the rudder force needed to contain this is the higher). This will
put a severe load on your leg in trying to keep the aircraft straight
and it is likely that you won't be able to contain it very long.
Personally I try to lock my knee over centre so that it is bone rather
than muscle trying to take the strain but I recall one flight when I
could feel it was going to give - and I know I could not have done
anything to stop it. Not a pleasant feeling.

The warning about not turning towards the dead engine is a little more
flexible in that, if really necessary, you could do this but only very,
very gentle turns only. It is far too easy for the aircraft to slip
into a spiral dive in this situation so its really not recommended.

One point I'd like to make is based on my own observations and I must
add that it's not part of any official thinking. You may agree or
disagree as you wish - I add it out of interest.

Engine failures in twins are very serious matters and the track record
of survivability isn't good. It's true to say that many accidents in
the past have started off with an engine losing power (or partially
failing) and with the aircraft going into the deck a few moments
afterwards. In my research through many such cases a pattern emerged
that showed the cause of the accident was not the engine failure itself
but loss of control of the aircraft following the failure. Most post
impact investigations showed one engine running at max power and the
other producing little thrust.

We all know the golden rule nowadays is that flying the aircraft is the
first priority in any situation. Too many perfectly sound aircraft have
flown into mountains or the ground because of distraction with others
tasks. This is horribly apt for twins because an engine failure needs
immediate cockpit action to correct the problem - if you don't do them
fast enough the unfeathered prop is going to end the flight very
quickly indeed (and I can assure you that it's bad enough when the prop
actually IS feathered).

The trouble is that just after take off you don't have enough time.
Lose an engine and things can go pear shaped in seconds if you don't go
through the drills fast enough. You MUST get the yaw contained
immediately (and at Vmca absolutely full rudder is required) and you
MUST get the dead engine's prop feathered. All the training is
concentrated on getting those drills done as quickly as possible and
you practise this again and again and again. Anyone spot the trap this
leads people in to?

In fact there are three traps and I've known good people (some were
good
friends) who have been caught out by all of them.

Trap one is the need for speed. Go through the drills as fast as
possible as it is essential to get that prop feathered before the oil
cools too much in the governor. This means you don't have much time to
identify the failed engine - and people have got this wrong. This has
caused a few accidents but isn't the prime killer.

Trap two is the mindset caused by the training. The focus is on getting
the aircraft into a flyable state as quickly as possible by containing
yaw and securing the engine. This diverts you from flying the aircraft
and it is here that most people get killed - they let the aircraft get
away from them. Far too many aircraft are out of control when they hit
the ground as pilots struggle to contain the failure.

Trap three is associated with the above. Because all the training is
dedicated to securing the dead engine and keep the aircraft in a
flyable state pilots don't consider the alternative.

Consider the condition right after engine failure. First the aircraft
is yawing rapidly owing to power differential plus the huge amount of
drag from a windmilling engine. In this state it is not going to stay
in the air - full stop. No aircraft can stay airborne with an
unfeathered prop as the drag is just too much. Full rudder is needed to
contain the yaw (the aerodynamic problem) but then the pilot has to
take his eyes away from the windscreen to sort out the engine problem
and get it feathered.

It is here that the accident sequence really begins because once your
eyesight moves away from the windscreen you have lost any clues as to
how the aircraft is behaving. You won't notice that yaw or roll has
begun again and it only needs a second or two to put the aircraft in a
non recoverable state. By the time you look up again it may already be
too late.

The sole reason for loss of control is lack of visual perception - the
aircraft is entering a non recoverable position because you are too
busy to see it happening. You can't help this as you have to get the
engine feathered - but with the aircraft on the edge of the flight
envelope with full rudder needed this is the worst moment to be looking
away.

What if you took the yaw problem away so that you could sort the engine
out without fear of losing control? Without yaw the aircraft would be
stable enough to give you the few seconds you need with your head
inside to sort the controls out.

I wonder how many twin pilots would actually think about reducing power
on the live engine? To me the loss of control is directly attributable
to the forces produced by the live engine running at full power.

Yep - it sure depends on height but the truth is that if you are so low
that you can't get the prop feathered anyway then you are still going
to be facing a forced landing. A twin with both engines closed is far
more flyable than one with asymmetric power.

If you are a little bit higher then you'd go for the shutdown routine.
To really be safe though you would have to look outside a few times
whilst securing the engine to ensure the aircraft wasn't getting into a
dangerous attitude. This is difficult with both full rudder applied and
your attention then diverted on the shutdown routine and pulling all
the right levers. Until all this is done the aircraft is still going
downhill.

If you pulled the power back on the live engine then the rate of
descent will increase - but not by a lot. You wouldn't have to apply
anything like full rudder and the aircraft would be far more stable -
it wouldn't be half as critical to take your eyes inside to sort out
the engine.

Just my own thoughts.

As to the big tin I'm sure they mostly do their engine failure cases in
the sim these days. For live training I suspect they could still partly
simulate an engine failure by bring back one engine to neutral thrust
but this wouldn't be of any value except for handling purposes (maybe
useful during an hold or ILS procedure to see what the pilot does). It
wouldn't produce all the system failures had the engine fully quit.

bones









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