Good discussion, William, and I agree. My experience with mountain flying has all been in fuel injected engines and I'm wondering if you can use the leaning the mixture (which gives you significantly more power at high density altitude) in an Ercoupe with a carburetor. Seems the mixture leaning is a pretty slow process in my Ercoupe; but I've not used it at altitude (shucks, have had the coupe for over 2 years and haven't been above 3,000 ft yet : >). Dan C
On Jun 9, 2010, at 10:45 PM, William R. Bayne wrote: > > 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) > > -- > > 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 >> >> >> >> ------------------------------------ >> >> Yahoo! Groups Links >> >> >>
