Hi Dennis,
You don't say what prop you have, but I will assume it is the correct
size metal McCauley of "standard" pitch.
If so, several considerations. You will have slightly better
performance (for a given temperature) than the 415-D figures (1)
because you will be 80 lbs. lighter, because the metal prop has
slightly better efficiency (which slightly increases the resulting rate
of climb) and because I am consulting the take-off figures in the 415-E
Flight Manual (because you have the 85hp engine instead of the 75hp in
the D).
I have crossed the Continental Divide several times each way flying
from Phoenix via Lordsburg (the southern route) or to Albuquerque (the
northern route. Fly the mountains early, because afternoon
thunderstorms build fast and often in the afternoon heat...not a good
time to be there, aside from the turbulence.
This was infinitely more challenging utilizing VOR and pilotage than
GPS today. VOR coverage below 10,000' in that area is poor, so one had
to achieve accurate enough results with pilotage (despite iron deposits
influencing the compass) after leaving Phoenix VOR reception to
intersect the rather limited "circle of VOR coverage" of the few VORs
en route to Albuquerque.
With a normally healthy engine, the "book" (interpolated) suggests an E
model with a wood prop at 1400 lbs. and 100ºF will require 4513' of
runway before liftoff. That isn't the "whole story", though. You can
lift off in "ground effect" on a given day (few air masses are exactly
the same) and find the plane won't climb and loses altitude in the
gentlest bank. That can put you in deep yogurt real quick, so
carefully review conditions in depth before deciding to take off and
never attempt a takeoff in which success is at all doubtful. This is
easier said than done.
Again, with reference to 415-E data, the chart interpoation suggest a
climb rate at 4500' PA and 100ºF of 282 FPM at best rate of climb. I
am NOT bragging in revealing dodging a church steeple well away from
the Lordsburg airport because our rate of climb had essentially ceased
at 90 mph and 100' off the ground. Instead of establishing my normal
"cruise-climb" I should have set the plane up for best rate of climb to
get higher under those conditions. Another time, departing Albuquerque
near noon I found terrain rising more rapidly than we were in three
possible directions. A "trick" I discovered that day is to look for
buzzards and/or cumulus clouds. These mark rising air, and the boost
in climb is free except for the time off course and circling upward in
a stationary thermal.
It is not unusual to find an inversion over an airport, in which the
air temperature actually rises as you climb. Such a "cap" of air is
what traps smog in the Los Angeles, CA basin. Once through that "cap"
with the superheated air nearer the ground (which typically has less
"lift" in it) below you, climb performance is much better.
Where there is rising air there is also sinking air. Always approach
higher ground at a 45º angle so you can turn away with only a 90º turn
should you encounter a downdraft there to maintain good terrain
clearance. We had to search up and down a high mesa on our course to
find more lift, but eventually climbed to over over 10,000' that day en
route to Dalhart, TX and East.
It would suggest you plan your trip to arrive at the airports you speak
of late in the day and depart in the early morning. That makes a big
difference because high altitude airports usually enjoy low humidity
and that gives you 60ºF early morning takeoff conditions before an
afternoon high of 100ºF. Alternately, depart with just enough fuel to
get to a lower airport before filling the tanks. If you calibrate your
tanks, keep records of your fuel consumption, and monitor it several
times each leg this is quite predictable and safe. In good VFR
conditions, half the nose tank's usable fuel is plenty of reserve
(unless you are simultaneously learning use of the GPS on a given
flight ;<)
Taking off from lower but hotter airports in Arizona in the summer, I
have taken of with full fuel and left my wife on the ground to see how
much "lift" is in the air mass present. Unfortunately after returning
to get her, the engine is thoroughly "heat soaked" and oil temperatures
can get a bit dicey before reaching cooler temperatures aloft.
Fortunately today's oils continue to lubricate adequately at
temperatures above redlines still recommended for our little
Continentals.
There are options available to the proficient and knowledgeable pilot
that can greatly increase the utility of relatively low performance
aircraft.
At some point experience significantly reduces the big bag of luck that
new pilots dip into frequently. But knowledge and quick thinking is
the best "insurance". These are the words of a Private Pilot, not a
CFI or professional aviator. Results may vary.
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
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On Jun 9, 2010, at 13:03, Dennis wrote:
My brother & I are planning a cross country trip (with my 85hp 415C)
which will require one or two take offs at airports with altitudes
4000 to 4500 feet and temperatures up to 100 degrees F. Density
altitude probably at about 6500 feet or possibly higher. Runways are
6000 feet long and the Ercoupe will be loaded to maximum at 1320
pounds.
Considering all the above information, the 415-D flight manual charts
(pages 10 and 11) show that it will take 3950 feet to take off and we
will climb at 330 feet per minute. My problem is that I have never
done this. My normal take off roll when I am alone and it's 70
degrees F. takes me 1000 feet or less. What I really need is someone
who is very experienced in these long take off rolls to help convince
me that the Ercoupe will really take off at 3950 feet and then climb
at 330 feet per minute. Of course, if it isn't at take off speed at
3950 feet of the 6000 foot runway, I still have time to abort the take
off.
I will really appreciate any information or advice you can provide.
Thanks, Dennis Hatfield
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