First please don't shout. It's rude.
Second I know you said "touchdown speed." The problem is that,
as I said "someone taking the words at face-value might
interpret" this to mean an over-the fence speed in the
60's. Unfortunately, this isn't too far off what's in some
of the literature that came with the Ercoupe at various
times. And if you still have the original 'owner's manual'
from when your 415D was a 415C, the orange, and black
and white one, that advice is in there, as I recall.
Given that, at least anecdotally, more mechanically sound
Ercoupes have come to grief by the pilot error of landing
hard after a too-slow approach, we 'high time' Ercoupe
guys have a responsibility to be very clear about the
fact that 'speed is safety' until you're right down in
the round-out and flare.
Third I really don't give a monkey's for that 1.3 * minimum
flying speed stuff in the Ercoupe. We all know the
1.1 for short field and 1.3 for a normal approach
rules of thumb. Those are for normal aircraft with
elevators which are strong enough that they can
be made to flare unless they're so far in the hole
that there's no salvation for them.
In an Ercoupe with a wimpy 9 degrees of up-travel on
the little narrow non-split elevator, the elevator can
easily be out of business a lot earlier in the process.
You don't know that until you feel *klunk* as the yoke
hits the stop and notice, to your horror, that it has really
had no effect on the nose-down attitude.
(The other side of the equation is that an Ercoupe *can*
be landed successfully at cruise speed without
bouncing off into the stratosphere. If the landing
gear is right, and the tail is where it belongs, it's
a non-event. I've put down as high as 90MPH at
a big regional airport to help the traffic behind me,
and it was just fine.)
I frankly don't know what my 'minimum flying speed
is.' I can't get that slow. The ASI is bouncing around
55 or so, but she's really still flying. Sinking, bad,
but flying. I can put the power on, but then she
speeds up. If I kill power and haul the nose up
quickly, she'll nose over, but I'm not sure if that's
just the elevator giving up since there is no buffet,
and again the ailerons are still in business in
the normal fashion.
I say, "burn that equation" for an Ercoupe. The
way to determine your approach speeds is to
make some patterns with long-ish finals, to give
you time to really look:
1) Learn to recognize what sink looks like on approach.
If you've flown Tri-Pacers or fat-wing Cherokees, or
even Cardinals, you know. If you've flown 150's and
172's, you may not. This is the region where pitching
up more causes you do go down faster. It is the region
where, if you drew a line down the fuselage to the ground,
you'd hit the ground short of the point where the line
intersects it. It has a definite visual aspect, because
your angle of approach starts to decrease without your
doing anything!
2) Start flying your finals around 85 (assuming you have
2000 feet of runway). Recognize you'll waste some
runway, but use the time to get used to the very
light pitch-forces. Do this power-on, that is with
your normal 1400-1700 RPM, descent value. We
choose 85 MPH IAS because there is almost no way to
get in trouble at this speed, even if you're distracted
by the open canopy, or by the unfamiliar light controls
or by the novelty. Unless you run off the end, which
would be hard to do with anything more than 1800
feet. When you're tired of floating...
3) Drop down to 80. Enjoy the shorter landings and
the fact you now have some options. Learn to
ease it down for a 'greaser' or hold it off for a
decisive 'plant.' You'll need both skills. By now,
you're getting the feel for the pitch on this Coupe.
They aren't all the same.
4) Start easing down about 2MPH at a time.
5) Note the speed at which the airplane is getting
sinky. Etch that in your brain as the "no-slower-than
this down final" speed.
6) Add about 5MPH to this 'drop dead' speed in the event
of a power-off approach (i.e., you were too high and closed
the throttle entirely, or the engine is dead). 'Power off'
means less than 1200 RPM. At 1300, the Coupes seem
to add about 5MPH to the speed at which they will fall
behind the power curve.
7) Add about 2-3 MPH to your 'drop dead' speed for your 'short
field' power-on landing speed. Set that speed, but don't ride
the ASI, watch for sink and keep adjusting it out with power
and pitch. This will result in some very short landings.
8) Add about 7MPH to the 'drop dead' speed for your normal
'power on' approach speed. Chances are that number will
fall between 75 and 80. In this band, in any case, it's
amazingly non-critical, except that every 1MPH costs
you maybe 50 feet of runway.
9) Remember that 'drop dead speed?' It can be useful. If you're
real high on final, and you have no rudder pedals, and you have
no flaps, and the canopy is shut so you can't get your arm out,
then drop down to it early in the game. You'll quickly sink towards
the glide-slope. As you APPROACH the glide slope you should
pitch down decisively to a little above your desired approach
speed. Breaking the sink in an Ercoupe requires decisive action
and a bit more altitude than expected. Don't do this on short
final. Go around. On short final you may not have time to arrest
the sink. This could be embarrassing, as you will run out of
airspeed, altitude, and ideas all at once (actually there is one
last idea, and that is 'full throttle' which will usually pull you
out of the hole you're about to dig in the end of the runway).
Add what you want for gust factor. Bearing in mind that it's better
to add too much (the wind shortens the landing anyway) than too
little and to end up behind the power curve. The Ercoupe is really
stunningly agile in the landing phase, and if you're an active pilot
(not just one of those flare-and-pray types) you can easily make
lovely little corrections right down to touch-down. Much more so
than other airplanes where the ailerons have turned to mush.
The multiplication tables be damned, this is the only way I know of
to really understand how to land a particular Ercoupe with the
vagaries of pitot-static systems and the slew of modifications
which make every one unique.
Greg
At 02:58 PM 7/8/2004, Ed Burkhead wrote:
GREG
I DIDNT EVEN READ YOUR ENTIRE MESSAGE BEFORE ANSWERING BECAUSE YOU DIDNT READ MINE!
I SAID **** TOUCHDOWN **** SPEED!
If youve read the messages Ive sent over the years, Ive 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 airplanes minimum flying speed. YOU COULD SEE FROM MY MESSAGE THAT I SAID **** TOUCHDOWN **** SPEED is below 60.
I CANT 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 whos 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. Whats 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, theres 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 models 47-52 mph touchdown with 13 degree up travel.
Anyone who cant 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
