Hi Dan,
The Ercoupe Instruction Manual should be owned and familiar to every
owner, but read (as all manuals) with enlightened awareness.
When it says that "It is acceptable to cruise up to the red line placed
on the tachometer dial at 2275" (rpm), I then presume two things. 1.
It was written for postwar Ercoupes with the C-75 engine, and (2) for
those with 85hp, it is equally "acceptable to cruise up to the red
line..." of 2575 rpm (where the red line should be placed on the
tachometer dial of those Ercoupes.
If anyone believes that is abusive to the engine, I'll gladly explain
why it should not be.
On the subject of leaning (for the Stromberg carburetor then standard),
it says: "At altitudes above 5000 ft., the decreased density of the
air may cause the mixture to become too rich for best power. This may
be investigated by moving the mixture control from full-rich position
while checking the constant load rpm. If the rpm does not increase as
the mixture is made leaner, the control should be returned to the
full-rich position. For average operation below 5000 ft' altitude, the
carburetor should be left in the full-rich position When at part
throttle, the fuel consumption may be improved by leaning the mixture,
but in no case should the control be moved far enough to decrease the
engine rpm. The control should always be moved back to full-rich
before any change in throttle setting."
As John says, the CHT does not respond as fast as the EGT when leaning.
That does not mean that it does not provide useful information. The
fuel-air mixture going to the separate cylinders of our little
Continentals is not as equal between them as it is in the bigger
engines (or those with fuel injection). It is now known that
increasing the temperature of the mixture from the carburetor improves
fuel vaporization. This improves the equality of the mixture between
cylinders. You do this with judicious use of carburetor heat.
In cruise, a CHT will allow the pilot to verify the decrease in the
difference in temperature spread between the cylinders as carburetor
heat is added. We're talking of a small amount of carb heat here,
inasmuch as the warmer air is less dense and an engine begins to
produces less power from the point that the effect of the improved
vaporization is overcome by the reduced density of the warmer mixture.
While most of us learned in pilot training to never use partial carb
heat, I believe this to be a valid exception. The amount used is very
small and should have absolutely no effect on the amount of heat
available to when "full carb heat" is required and applied to clear
carburetor icing. It may, however, reduce the frequency with which
carb icing is experienced because ice is slightly less likely to form
in the slightly less cold mixture.
That said, we now know about pressure altitude. If that had been as
well understood when Fred Weick wrote this manual, he likely would have
used the term "density altitude" in his manuals instead of "pressure
altitude". Since the engine is not aware of it's distance above the
ground, but only of the amount of fuel and oxygen in each charge of
mixture supplied each cylinder, we now know that 5000' "density
altitude" can occur during the summer at significantly lower
elevations.
I believe John's point was that above 7000' "density altitude" there is
insufficient power available for mixture "mismanagement" (i.e. if one
were able to achieve optimum "lean of peak" operation) to damage the
engine in cruise. That may not be the case between 5000' and 7000'
"density altitude".
Regards,
William R. Bayne
.____|-(o)-|____.
Copyright 2010)
--
On Jun 10, 2010, at 16:59, Paul Drake wrote:
May i inquire as to the proper method for leaning without egt or cht?
Thanks Paul Drake
--- On Thu, 6/10/10, William R. Bayne <[email protected]>
wrote:
From: William R. Bayne <[email protected]>
Subject: Re: [ercoupe-tech] Take off distance & climb rate
To: [email protected]
Date: Thursday, June 10, 2010, 5:55 PM
Hi Dan,
Thanks for the kind words. I have always regarded the Ercoupe as a
fine cross country machine if one understands its capabilities,
limitations and their own limitations.
A properly functioning mixture control is absolutely necessary to
achieve maximum possible engine performance and efficiency at higher
altitudes. The procedure in the Ercoupe Instruction Manual works
fine, except that I have found benefit below 5,000' PA (where density
altitude at 100ºF may be 7,000').
EGT and/or CHT instrumentation is inexpensive (I used a single-probe
non-TSO EGT). One has access to much more important information with
sensors on all cylinders and a selector switch controlling a single
indicator for nominal additional investment. I believe intelligent
use of such by the pilot allow him/her to best achieve that magic
point where the "best power", "best economy and "best airspeed"
curves cross for a given coupe. I believe an engine so operated is
more likely to achieve or exceed TBO because the operator has the
ability to be aware of, diagnose and remedy many common engine
problems before their adverse effects accumulate to the point of
failure.
With the relatively low power-to weight ratio of the Ercoupe (as
compared to most "modern" certificated designs) proper leaning can
make the difference between success and failure taking off and
climbing out from high altitude airports in the summer. I should
have mentioned that.
To illustrate the "difference" our mixture control makes, My wife and
I once returned from somewhere and decided to overfly our airport and
continue to one near the beach for something to eat. That was
sufficient "break" from normal procedure that I forgot to return the
mixture to Full Rich before or during descent from "high lean cruise"
position. Engine performance seemed normal until I reduced power
for descent from pattern altitude to land and the "fire went out" in
the engine. Even though the prop continued "windmilling", that
transition was definitely a "holy s**t" moment.
Of course the power smoothly returned upon my timely but smooth
return of the mixture control to "Full Rich" (without backfire), but
it was a very clear reminder of the fact that a properly operating
Stromberg mixture control is effective to the purpose intended and
not to be ignored. I have also never forgotten to enrich in descent
again ;<)
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
--
On Jun 10, 2010, at 11:43, Caliendo Dan wrote:
> 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
>>>
>>>
>>>
>>> ------------------------------------
>>>
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>>>
>>>
>>>
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