A correction to my earlier post: When I put in the symbol º, on my
computer that is the "degree" mark, and that is what was intended.
Sorry if that confused anyone.
Ed, my hat is off to anyone who has accomplished an involuntary
off-airport landing. All I have done is avoid one once. But that was
enough to get me to think and pre-plan further. That process should
never cease for any of us.
With the considerable advantage of 20-20 hindsight, let's play "Monday
morning quarterback". If you were on a cross-country flight you likely
lost power at or above 5000' AGL? That would have afforded you much
more time to weigh options on the way down than would be possible had
it happened soon after takeoff.
If I believe I can glide to any point within an imaginary circle around
the plane circumscribed by where my line of sight over the wing tips on
either side hits the ground, that's as good as any point to start. A
gentle 360º turn is a necessary investment of altitude to properly
evaluate all potential landing sites, particularly over forest, desert,
water or mountain terrain with few good options. The original "range"
can be revised to improve accuracy if need be as the descent
progresses.
You had "gleaned" a "mass of printed material in magazines and such"
before your first "hands-on" Ercoupe experience. I'm impressed that you
had the 70 mph figure because a the good information in such sources
must be somehow separated from the bad. Any meaningful evaluation or
discussion must have some common basis, and that, to me would be the
true airspeed at which the airplane is operating. If you prefer a 5 or
10 mph additional as a "fudge factor", fine; but there are ASIs "out
there" that read high too. A guess seems appropriate in aviation only
when all else fails.
You intended to glide at 70 mph but were actually gliding at 55 mph.
That's 3 mph less than the published stalling speed for your 415-D.
The road to [failure] is paved with good intentions. No instrument can
be trusted until it is verified. I agree that every instrument should
be verified before trusting it, and that 1.4 times 58, or 81+ mph TIAS
would be a very conservative approach speed. I don't know how close it
is to "best glide speed".
Today it's easy to verify an ASI reading with GPS. That should be a
high priority during climb out following takeoff in a strange bird
followed by GPS verification of "minimum speed". In that context I see
no valid reason to increase our 70 mph TIAS; but the hairs we're
splitting here are pretty fine.
Any reasonable airspeed indication one picks for setting up their glide
is but the beginning of the process. Not the end. Once in a stable
glide, try 5 mph more. If the VSI (or altimeter) suggests the sink
rate has decreased, try 5 mph more. When you find it, stick with
minimum sink unless your spot is into a brisk wind (in which case you
might want to add 5 or 10 mph). Achieving maximum glide range is the
highest priority until the field is "made". What the ASI says is just
one piece of the puzzle. Even without a Vertical Speed Indicator, you
had plenty of time to determine rate of descent with the altimeter,
although it would require nerves of steel to do that after a power
failure. I remain amazed at how few VSIs and Altimeters in the same
plane agree (if one compares a pilot's written impression of the VSI
over a given minute with the change in altitude per the Altimeter).
I would speculate that you set your trim for your glide in the full
back, or "Land" position. Per Ercoupe Service Memorandum No. 38, Par.
11.b.(3) NOTE your bird should have been flying between 65 and 75 mph
(if properly rigged). While trim movement is not listed in Aircraft
Specification 718 for the 415-C or CD, the rigging instructions for the
415-C (and, presumably the 415-CD) in ESM 38 are consistent with
specified trim range shown for the 415-D in ATC 787 of 0º up and
60º down. The change in trim/elevator position I would expect to be
identical between these three models. I therefore suspect that your
bird was not rigged so as to glide in the appropriate speed range (but
I don't doubt you believed it to be "airworthy").
I'll bet when you drive on icy roads, or after the first rain wetting
the road after a long, hot summer, you "test" your brakes for
efficiency each time you approach a stop sign and slow down more than
usual. If you had similarly "tested" available up elevator and found
none there you would likely have lowered the nose and carried more
speed all the way down. The yoke had to be near or against your
stomach which, in and of itself, might have suggested that things were
not as they should be. We must keep in mind that a 415-D's yoke is all
the way back at 9 degrees "up", whereas 415-C and CD models have four
more degrees of "flare" available. Your experience was one where the
difference had significance.
Jerry, how important is any difference between Vmin sink speed and Vl/d
in an Ercoupe? If instrument readings are not accurate how do you
establish and confirm Vl/D? If you lost power on your way to Bermuda
and wanted to avoid becoming shark bait as long as possible you might
want Vmin sink speed. On the other hand, if you have a boat in sight
you might need Vl/d. While the latter would seem more immediately
applicable to the great majority of scenarios likely flying over land,
I would speculate that as long as lowering the nose and speeding up the
plane results in a lower rate of descent you are best off doing that.
I seriously doubt slowing to "best angle of climb" speed in a glide
would improve glide range.
A successful unintended landing following a power failure is NOT a
static situation but a dynamic one that may continue to change all the
way to touchdown. Once you've mentally committed to a specific landing
spot, you do whatever is necessary to touch down near the beginning of
usable space at the lowest speed and rate of descent consistent with
available options, knowledge, experience and ability. You have to play
the cards you're dealt. It's NOT a "one size fits all" solution.
While, admittedly, here on the list we are preaching to the choir, we
DO get some newbies. A problem that never goes away is that new or low
time Ercoupe pilots have very little "frame of reference". I think we
owe them our best efforts to dispense wisdom over confusion and facts
over speculation whenever and wherever possible. Mere reading does not
enlighten one to the full extent of the considerable performance
information ERCO worked out and documented. I found it well worthwhile
to visualize being in the cockpit at the controls observing how
instrument readings and the "feel" of the controls change with each
described trim, yoke, mixture, throttle, or carb heat change.
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
--
On Aug 3, 2010, at 20:32, Ed Burkhead wrote:
Bill Bayne wrote:
> Let's assume, however, you just bought a coupe and need to
> fly it home. With absolutely no experience in that bird you
> need a number to have in mind before takeoff.
>
> Bart said "70 [mph] is close. I think." I agree with him.
OK, I’ll sort of agree but I think the number to have in mind before
the first takeoff in a newly purchased Coupe is 75, not 70 and I’ve
got personal experience with that scenario as a reason.
When I bought my Coupe, on the first day, I did the basic three
takeoffs and landings to a full stop and all was well. The next day,
I did a two hour or so cross country, the ice in the bottom of the
tanks melted and refroze in the fuel line blocking fuel flow.
Gliding down, I USED the number of 70 mph as that was my best gleaning
from the mass of printed material in magazines and such – my only
Ercoupe transition training.
When it came time to flare for touchdown I found there WAS NO FLARE AT
ALL – I had already been within a fraction of an inch from full aft
yoke. The plane just leaned back a bit and WHUMP, WE HIT HARD.
Fortunately, the plowed field covered with packed snow gave just
enough but was firm enough that no damage resulted at all. That was
pure blind luck. Had the surface been any harder or softer, major
damage probably would have resulted.
I needed that extra bit of airspeed for a flare and didn’t have it.
The airspeed indicator was about 15 mph off in that low airspeed
range.
So, I’ll assert that before you do your first takeoff, decide that
your first takeoff emergency glide speed will be either 75 or 80.
As soon as you get well up in the air ON THE FIRST FLIGHT, find out
the minimum flying speed as claimed by that ASI, multiply it times 1.4
and use that for your best glide speed / approach speed until you can
do further testing.
That’s my story and I’m sticking to it!
Ed
