* Two texts (the first one is very long, and is shortened here) to enlighten the subject of piloting and training for upsets.
Jacques Rosay chief test pilot « Safety First » magazine
Typically, in cruise at high Mach number and high altitude, at or
close to the maximum recommended FL, there is a small margin
between the actual cruise AoA and the AoA STALL. Hence, in
ALTERNATE or DIRECT LAW, the margin with the AoA SW is
even smaller.
The encounter of turbulence induces quick variations of the AoA.
As a consequence, when the aircraft is flying close to the maximum
recommended altitude, it is not unlikely that turbulence might
induce temporary peaks of AoA going beyond the value of the AoA
SW leading to intermittent onsets of aural SW.
Equally, in similar high FL cruise conditions, in particular at turbulence
speed, if the pilot makes significant longitudinal inputs, it is not unlikely
that it reaches the AoA SW value
The AoA decrease may be obtained indirectly by increasing the speed,
but adding thrust in order to increase the speed leads to an initial adverse
longitudinal effect, which trends to increase further the AoA
It is important to know that if such a thrust increase was applied when
the aircraft is already stalled, the longitudinal effect would bring the
aircraft further into the stall, to a situation possibly unrecoverable.
Conversely, the first effect of reducing the thrust is to reduce the
AoA
UPSET RECOVERY A Test Pilot’s point of view. (FAST N°24) by William Wainwhright Chief Test Pilot Airbus Speaking of stalls and the airline pilot’s training.
For the training managers from American Airlines, Delta, and United,
the only thing necessary was to give an overall industry approval to their
existing programmes; they already worked, because the
many pilots that had undergone training all came out of it with
the same standardised reactions to the standard upsets. For them, this was the
necessary proof that their training programme worked.
Where we differed was in our conviction that there is no such thing as a
standard upset and our reluctance to endorse simplified procedures for recovery
from an upset.
We wanted a general knowledge based approach, as opposed to a rule
based one. For this, after proposing some initial actions, we talk about “additional techniques which may be tried”. This obviously is more difficult to teach.
Even those pilots who do stalls on airtests, as might be done after a heavy
maintenance check, only do them with gentle decelerations, and they recover immediately
without penetrating very far beyond the stalling angle of attack. There
is a world of difference between being
just before, or even just at, the stall, and going aerodynamically well into it.
ON THE USE OF SIMULATORS :
We manufacturers were very concerned over the types of manoeuvres being
flown in simulators and the conclusions that were being drawn from them.
Simulators, like any computer system, are only as good as the data that goes
into them. That means the data package that is given to the simulator manufacturer.
And we test pilots do not deliberately lose control of our aircraft just to
get data for the simulator. And even when that happens, one isolated incident
does not provide much information because of the very complicated
equations that govern dynamic manoeuvres
involving non-linear aerodynamics and inertia effects.
The complete data package includes a part that is drawn from actual flight
tests, a part that uses wind tunnel data, and the rest which is
pure extrapolation.
It should be obvious that firm conclusions
about aircraft behaviour can only be drawn from the parts of the flight envelope
that are based on hard data. This in fact means being not far from the centre
of the flight envelope; the part that is used in normal service. It does not
cover the edges of the envelope. I should also add that most of the data
actually collected in flight is from quasi-static manoeuvres. Thus, dynamic
manoeuvring is not very well represented. In fact, a typical data package
has flight test data for the areas described in Table 1.
In other words, you have reasonable cover up to quite high sideslips and
quite high angles of attack (AOA), but not at the same time. Furthermore, the
matching between aircraft stalling tests and the simulator concentrates mainly
on the longitudinal axis. This means that the simulator model is able to correctly
reproduce the stalling speeds and the pitching behaviour, but fidelity is
not ensured for rolling efficiency (based on a simplified model of wind
tunnel data) or for possible asymmetric stalling of the wings. Also, the range
for one engine inoperative is much less than the range for all engines operating
and linear interpolation is assumed between low and high Mach numbers.
Wind tunnel data goes further. For example, a typical data package would
cover the areas described in table 2. In fact, this is a perfectly adequate
coverage to conduct all normal training needs. But it is insufficient to evaluate
recovery techniques from loss of control incidents. Whereas, the training
managers were all in the habit of demonstrating the handling characteristics
beyond the stall; often telling their trainees that the rudder is far
more effective than aileron and induces less drag and has no
vices! In short, they were developing handling techniques from
simulators that were outside their guaranteed domain.
Simulators can be used for upset training, but the training should be confined
to the normal flight envelope. For example, training should stop at the
stall warning. They are “ virtual” aircraft and they should not be used to develop
techniques at the edges of the flight envelope. This is work for test pilots
and flight test engineers using their knowledge gained from flight testing
the “ real” aircraft.
Vereinigung cockpit, the German syndicate has issued a press release that says that blaming the pilots and only them is far too easy. (On their internet site, press releases)