Appendix

12 13
English
Approaching Quito – Historic Procedures
Aerosoft GmbH 2016
Preparation
Reduce your load; kick out those six-packs and your mother-in-law. Bet-
ter to leave them behind than to scatter them all over the last few feet
of the runway. Don’t fly with more fuel than is needed. Rule of thumb,
for every 10% under max gross weight, performance increase 20%.
Keep in mind that an aircraft like a Cessna 175 at 8000 feet only de-
livers 50% of its rated power. Above all, make sure your aircraft CAN
fly in the current conditions. A Piper Cub with a ceiling of 11500 feet
simply will not fly if the density altitude is 12000 feet. It simply will not
be able to lift off even if the runway is 20 miles. If the ceiling of your
aircraft and the density altitude come close together your margins of
safety decrease. You might need to wait for cooler conditions to fly!
Starting
Depending on the aircraft starting procedures will be different. In the
Cessna 182 you will need to pre-lean the engine and give a bit of
throttle to get the engine to start. Do not run at high power settings
for a long time because the engine might overheat. It is however a very
good idea to do a quick high power setting just before entering the
runway to make sure the engine will rev up without problems. Under
these marginal conditions you do not want to have an engine that does
not spool up fast and smooth. But keep an eye on the temperature!
On some aircraft the FSX “Auto Start” function ([CONTROL]-[E]) will
NOT start the engine at this altitude! You will have to manually start the
engine with the mixture leaned and a bit of throttle set.
Takeoff
The first thing to remember is to trust your instruments and above all
your airspeed indicator. Visual impressions might be misleading and the
point where you normally lift off might not be the point where you have
enough airspeed in a high density altitude situation! Do not use Short
Field flap settings as this most likely increase your takeoff run. Always
lean your engine for max performance before starting your take-off.
Make sure you understand that not only your takeoff run will be longer
as density altitude increases but also that your climb performance will
be affected.
Landing
Again, do NOT rely on your eyes but on your airspeed indicator. The IN-
DICATED airspeed is the only thing that keeps you aloft. But in the end
it is only the groundspeed that is different, the landing itself is actually
surprisingly normal as long as you use your engine to keep the correct
speed. The only real surprise might be the lack of any ground effect as
that seems to drop off over 5000’.
Be prepared to see everything go a LOT faster than you might be used
to and be prepared to use a lot more ground than normal. That is not
a major issue most of the time as mountain runways are often rather
long.
The real problems start when things go wrong. On a normal landing you
have almost all of your power to get you out of a problem, but at high
Density Altitudes you might not have much to use, and in the thin air
the difference between max speed and stall speed is very small.
If you’ve never flown at a high altitude airport before, the first time you
do you run a major risk because on your standard checklist there will be
the item [Full Rich Mixture]. Now if you do that at 8000’ you run a high
risk of the engine stalling on you. If you are lucky this will not happen
before the engines slows down on the rollout, but if you are unlucky it
will die on you before you hit the next item on your checklist. Make sure
you keep high rpm on the prop but it is easy to over rev the prop shaft
so keep the needle just under the red line.
How do I estimate the Density Altitude?
Actually the correct calculation is very complex and involves tables and
many variables, but as always in aviation there is a rule of thumb that is
close enough for almost any purpose:
Set your altimeter to 29.92 (1013).
Read the altitude indicated. This is your Pressure Altitude (pa)
Now find the closest figure in the first column.
In the correct temperature column you can read a good approxima-
tion of the current Density Altitude.