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GREG
I DIDN’T EVEN READ YOUR
ENTIRE MESSAGE BEFORE ANSWERING BECAUSE YOU DIDN’T READ MINE!
I SAID **** TOUCHDOWN
**** SPEED!
If you’ve read the
messages I’ve sent over the years, I’ve always said to DETERMINE the minimum
flying speed for THAT aircraft with THAT airspeed indicator and use 1.3 times
minimum flying speed for the APPROACH speed.
EGADS!
NOWHERE, NOHOW, NOWAY
would I advocate coming down approach at the airplane’s minimum flying
speed. YOU COULD SEE FROM MY
MESSAGE THAT I SAID **** TOUCHDOWN **** SPEED is below 60.
I CAN’T EVEN READ THE
REST OF YOUR MESSAGE BECAUSE YOU ARE TRYING TO COUNTER SOMETHING YOU **THINK** I
SAID EVEN THOUGH I SAID NOTHING OF THE KIND!!!!
Now, lets start over.
The 415-C with 13 degrees
of up travel gives a TOUCHDOWN speed of about 47-52 mph.
The 415-D with 9 degrees of up travel gives a TOUCHDOWN
speed of about 53-57 mph.
Anyone who’s been through
pilot training had better know that you approach with enough speed to have
energy for flair and to handle wind shear or gusts. The commonly given approach speed rule of thumb is 1.3 times
stall (minimum flying speed) plus half the gust factor (with nothing else added
for the wife and kids).
Math:
50 * 1.3 = approach speed
of 65 mph
55 * 1.3 = approach speed
of 71.5 mph
But START with the
minimum flying speed measured for THAT airplane with THAT airspeed indicator
and do all calculations for those numbers.
You say you fly the
normal approach at 80. What’s YOUR
minimum flying speed INDICATED by YOUR airspeed indicator?
Ed
Burkhead
http://edburkhead.com/
ed -at- edburkheadQQQ.com (change -at- and remove the
QQQ)
-----Original Message-----
From: Greg Bullough
[mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 1:06
PM
To: Ed Burkhead; Coupe-Tech
Subject: RE: [COUPERS-TECH] Model
C to D conversion paperwork
At 01:12 PM 7/8/2004, Ed Burkhead wrote:
Jeeze, Lynn, there’s no way the 13 – 9
degree change can make a 20 mph difference in touchdown speed. With my D,
the touchdown speed was around 53-55 mph compared to a C model’s 47-52 mph
touchdown with 13 degree up travel.
Anyone who can’t get their D model down well below 60 had better do some
airspeed indicator repairs.
I don't agree with Ed.
And I'm concerned that someone taking the words at face-value might interpret
it to suggest that they come 'over the fence' in the 60's and thus bend a
perfectly
good airplane.
The issue isn't whether the plane will FLY at well below 60. The issue is
whether there
is enough elevator authority to FLARE at that speed. And it is VITAL that you
be able
to flare if you are at a touch-down speed which is that low, because you've
been sinking
like a stone at anything less than 70. And arresting the sink in an Ercoupe
with its
under-cambered airfoil requires proportionately more time and power and/or
pitch down
than most planes. At 65 it's flying...sort of. Not particularly well.
Below 70, you are definitely 'behind the power curve.'
I don't really look at the ASI between flare and touch-down anyway...I look at
the runway.
My landings can be crappy enough without burying my head in the cockpit, though
I've done
a few that have caused me to want to bury it somewhere else.
Ironically, in a 415D, your touch-down speed may well be HIGHER if your final
approach speed is too low, because you won't have the elevator authority to
bring
the nose up to decelerate in ground effect. You will thus sink it on, nose down
or flat.
Believe me, feeling the elevator hit the stop while the nose is still pointed
down
and the descent rate is still around the 500FPM rate is truly a 'sinking'
feeling.
It has happened to me twice in some 400 hours of Ercoupe time. Once I managed
a go-round and the other time a bit of power changed it from a 'hard landing'
to a
'firm arrival.' Thank god for Belleville springs and well-serviced oleos!
With both of my 415Ds, I have found that if I want to land very short I can
come
over the fence at 72, having brought the nose uncomfortably high and held
around
1300 RPM +/- 100 to arrest the sink (the power makes the elevator work better
and also arrests sink). However, in that situation, if the power goes away, the
plane settles to the ground immediately. That means that if the engine died,
I'd
be short and probably land hard. I found this trick to be easier on N2906H
with it's vernier throttle, than on N99387 with a quadrant. Two quarter turns
on the 'tap' was the 'land now' signal :-)
I believe that the 415D has to be treated like a high-performance airplane,
perhaps
most like a Bonanza. Stay well ahead of the power curve down final, perform a
round-out and flare with plenty of energy in the airplane in order to guarantee
effective pitch-up, and that you are in a sink-free glide right into
ground-effect.
This introduces the risk of ballooning if you flare too quickly... ...just get
the
nose up and 'don't let it land.' If you do that, it will make you look
brilliant.
Yes, that means coming 'over the fence' perhaps a bit more quickly than
necessary. However, the Ercoupe is so light and slows down so quickly
that unless you're on a 1000 foot strip, you're still likely to be okay.
The numbers I use on short final are:
80 - on a normal day. This gives me plenty of cushion so sink isn't
an issue, and lets me choose at the last
moment if I want to
paste it on or do a 'greaser.'
85 - if it's gusty or if N40's wind-shear machine is cranking (This
speed causes me to float, but I prefer to sort
all that out over
a nice runway, and I still don't use 2000 feet).
75 - if I want to keep it short (good for well under 1000 feet)
72 - if I'm having some sort of short-landing contest (have been as short as
400
with 5 knots of wind,
200 with 10)
Once you're in ground effect, and nose up, then you can mess about with trying
to touch down as slowly as possible. You're safe and virtually guaranteed a
decent
landing. Mess around at slow speed anywhere at or above hangar height, and the
outcome is in question....
Greg
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