approach
I would like to add:
Good definition of exact what happens base to final many times:
http://avstop.com/AC/FlightTraingHandbook/CrossedControlStall.html
Good brush up info:
http://avstop.com/AC/FlightTraingHandbook/CrossedControlStall.html
One point that not all pilots realize is that they can easily be flying an
airplane they are unfamiliar with even if they have a lot of hours in
type????
How?? Flying in thinner air than normal. Add humidity, rarefy, or go up in
altitude, and or fly at a heavier weight.
I have many more hours flying a 4 foot electric model than I do acting as
PIC of full scale. It is a unique electric model where the same wing is
used but have different electric power sources (Quick Sticks). AUW can
range between 19 oz to 46oz. That is a big change. There is not very many
times out where I don't spin it at least a few dozen turns with varying
AUWs.
When I was perfecting my flying and Quick Sticks, there were times with
the same AUWs, same CGs where I could not get into a good fully developed
spin?? Then there were times I would inadvertent enter a spin that was
unrecoverable??? It was kind of like the tail that wags the dog with me
fooling with changing the CG to tweak.
Variable was thickness of air!! Heavier usual will enter a spin easier,
and harder to recover for a given CG and air density.
Worst case is thin air, heavy and aft CG. Thin air on my model has the
greatest effect.
Just because you practiced spins on a 172 at 68 degrees 2 people and half
tanks, gives you way too much confidence with 4 people at gross, and 90
degrees at 2500 feet AGL with high humidity.
Here is reason why. Lets say you put an airspeed indicator on the rudder
of a 172 facing 90 degrees to rudder where we can measure airspeed
sideways in a spin. Lets keep the weight the same and CG the same in 2
scenarios. First lets let a spin fully develop into a 1000 foot deep hole
in Death Valley when it is 50 degrees below zero and a dew point of 100
degrees below zero, airspeed indicator would normalize at lets say 20
knots. Then lets go up to 18,000 feet where it is 110 degrees with a dew
point of 100 degrees. (Our 172 is a XXP with a 450HP PT6 turbo prop, and
airframe is constructed out of unobtanium so AUW is the same as a 180HP
Hawk) and let a spin fully develop, the airspeed indicator would normalize
at, you guessed it, 20 knots???
The difference is in Death Valley you would most likly be spinning less
RPM than a Cub on a normal day at sea level, but at 18K would be spinning
faster than a maple leaf could ever hope for. At 18K the a spin will much
more easily develop without trying, and once entered since the rudder is
most likely no where near effective enough to allow a recovery. Add more
to AUW, much worst, and go aft CG even much more worstererer.
One thing I use in models, and since so successful with models, full scale
as well is a pseudo eyes off, ears off airspeed indicator, stall
prewarner. Simple stupid. Do a very slight pitch up. That's it! When you
know your aeroplane, by doing this you can tell when response is sluggish,
you are getting close to stall. Great aid for final flare, steep turns or
when flying downwind where your ground speed can fool you into thinking
you have plenty of airspeed. After a while it is second nature, kind of
like counter steering on a motorcycle to avoid a threat. It will never
trick you like fast ground speed could when the wind shifted 180 degrees 3
seconds before touchdown and is giving you a tailwind. Works too with
roll, when in steep turns at lower speeds, you can feel ailerons begin to
get mushy, if you did nothing more than lower the nose you can feel much
more better response.
Works great on models when you are not in plane, works great when in
plane.
Remember nobody says you need to keep altitude when making turns, practice
up high, and try doing the worst things you can to enter a spin, and see
by just dropping the nose a little how much harder it is to enter a spin.
If you fly by using throttle to control altitude, and pitch to control
speed, if you overshot center line, go ahead and make a coordinated turn,
just don't pull back as hard as you need to maintain altitude, drop nose a
bit, you will gain a bit of airspeed, you will not pull as many gs but
most important keep your angle of attack lower. Add a bit of power and
sort when wings are near level. If you don't have enough runway to sort
out just go around.
If in a coordinated steep turn, if you must roll out quick, dropping the
nose helps a lot as well to prevent the low wing from stalling.
My main point for all this rambling, is try all this testing not just in
thick air, try it in thin air and heavy. You may realize you are flying
something that is very different from what you are expecting to be flying.
Ron Parigoris
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