The danger of assumption

On Tue, 13 Sep 2005 13:47:19 GMT, "Jay Honeck"
wrote:

Usually the plane just "flies itself off" the runway in this
configuration -- but not that night. Conditions of flight were fairly
unusual, for us -- the back seat was empty, no wind, high humidity, fairly
light on fuel -- so I suppose it was just pilot error.

It might be worth considering the possibility that something about the
rigging has changed. An extra-careful preflight or even a trip to the
shop may be in order. If someone has backed a truck into it while it
was parked, the damage might not be immediately obvious.

I've had dragging brakes produce interesting effects when breaking
ground.

RK Henry

It might be worth considering the possibility that something about the
rigging has changed. An extra-careful preflight or even a trip to the
shop may be in order. If someone has backed a truck into it while it
was parked, the damage might not be immediately obvious.

Everything checked out normally before flight.

I've had dragging brakes produce interesting effects when breaking
ground.

Low tire pressure changes things pretty dramatically in our plane.
Take-off performance suffers a surprising amount, for one thing.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Jay Honeck" wrote in message
news:HLAVe.346894$xm3.194258@attbi_s21...

It seems odd, however, that we *both* made the same mistake, which leads
me
to wonder if there was something atmospheric going on...

Thoughts?

My first thought was that perhaps you have less power than you usually do,
causing you to hang at the rotation speed a little longer than usual. Did
you rotate by the same point as you normally do? Other things: Mag check
normal? Normal RPM on takeoff run?

-Trent
PP-ASEL

My first thought was that perhaps you have less power than you usually do,
causing you to hang at the rotation speed a little longer than usual. Did
you rotate by the same point as you normally do? Other things: Mag check
normal? Normal RPM on takeoff run?

Yep, everything checked out during preflight and run-up. The JPI EDM-700
engine analyzer showed 6 good bars (meaning all six cylinders were firing
normally) manifold pressure was 26-27, and RPM was nailed right at 2650 or
so at full throttle.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Jay Honeck" wrote:
Here I had assumed that she was holding it down too long before rotation --
but it had now become apparent that she (and I) were in fact rotating
prematurely. Wind conditions were calm, temperatures were in the 80s,
humidity was very high, and a ground fog was developing as we landed.
Otherwise, everything was done according to Hoyle, with 2 notches of flaps
set for take-off.

Usually the plane just "flies itself off" the runway in this
configuration -- but not that night. Conditions of flight were fairly
unusual, for us -- the back seat was empty, no wind, high humidity, fairly
light on fuel -- so I suppose it was just pilot error.

Is there a reason why you *shouldn't* rotate at the published rotation
speed? ... more precisely, is there a reason why continuing the takeoff
roll beyond the published rotation speed before lifting off is not safe
(assuming you have enough runway ahead of you)?

In the C152, rotating at the published rotation speed nearly always
produced nice, smooth takeoffs. I recently bought a Shinn/Varga (low
wing, tandem, stick, trike), and in early flights, rotating at the
published rotation speed often produced a couple of seconds of "can't
decide if I'm really ready to take off and start climbing" hesitancy on
the part of the airplane (and yes, everything checked out during run-up).

We then tried letting it continue the takeoff roll beyond published
rotation speed, not really "rotating", but pulling back just enough to
take the weight off the nosewheel and letting it lift off in its own
time. Presto, all the takeoffs have been nice and smooth ever since, and
once it lifts off, there is NO hesitation to begin the climb. How far
beyond published rotation speed it lifts off, using this technique,
varies depending on temp, humidity and weight.

Other than runway length concerns, is there a reason why this technique
would not be preferable to abruptly rotating at the published rotation
speed?

Other than runway length concerns, is there a reason why this technique
would not be preferable to abruptly rotating at the published rotation
speed?

Particularly with low wing airplanes, this can produce a wheelbarrowing
effect where your mains get light, and even lift off, but you are holding
the nosewheel on the ground. Not good for the nose gear and any crosswind
gust could produce some rather interesting and dangerous effects.

Jim

In article ,
"Jim Burns" wrote:

Other than runway length concerns, is there a reason why this technique
would not be preferable to abruptly rotating at the published rotation
speed?

Particularly with low wing airplanes, this can produce a wheelbarrowing
effect where your mains get light, and even lift off, but you are holding
the nosewheel on the ground. Not good for the nose gear and any crosswind
gust could produce some rather interesting and dangerous effects.

With two notches of flaps and two adults in the front seats, your center
of lift was way aft and your center of gravity was way forward. Think
about it.

With two notches of flaps and two adults in the front seats, your center
of lift was way aft and your center of gravity was way forward. Think
about it.

I've never flown a Cherokee 235 before, but in the 140 thru 180 models,
but on a paved runway, leaving the flaps fully retracted during the
takeoff roll and kicking in the first notch at rotation always made for
a very good-feeling solid takeoff. I prefer to begin rotation at Vx to
ensure plenty of flying speed. The Cherokees don't seem to eager to
leave the ground until you've got that much airspeed anyway.

I've never flown a Cherokee 235 before, but in the 140 thru 180 models,
but on a paved runway, leaving the flaps fully retracted during the
takeoff roll and kicking in the first notch at rotation always made for
a very good-feeling solid takeoff. I prefer to begin rotation at Vx to
ensure plenty of flying speed. The Cherokees don't seem to eager to
leave the ground until you've got that much airspeed anyway.

Well, today we flew to Davenport, IA. A cold front had come through last
night, and all of that thick, hot, juicy air is back down south (where it
can *stay*), leaving behind cool, crisp, clean, lovely Canadian air in its
wake.

Wow, what a difference! It's like having 100 extra horsepower! We
literally jumped off the runway after an incredibly short roll, and were
soon climbing out at 1500 fpm. No skipping down the runway this time, even
though the weight and configuration were exactly the same.

Of course, with everything all stirred up by the frontal passage, the air
was rough as a cob, but visibility was a zillion miles. Once we got to
altitude it was smooth and drop-dead, take-your-breath-away beautiful.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jim Burns wrote:
Other than runway length concerns, is there a reason why this technique
would not be preferable to abruptly rotating at the published rotation
speed?

Particularly with low wing airplanes, this can produce a wheelbarrowing
effect where your mains get light, and even lift off, but you are holding
the nosewheel on the ground. Not good for the nose gear and any crosswind
gust could produce some rather interesting and dangerous effects.


I think you missread what he wrote: not rotating is a far cry from holding it
down. When I accelerate in a Cherokee, I hold the yoke neutral until I'm ready
to fly, then rotate and fly off immediately. In a Cessna, I ease the yoke back
once I'm at or beyond stall speed and let it fly off when it's ready.... rolling
on the mains only until it is.

I would agree holding it down is a poor practice.



--
Mortimer Schnerd, RN

VE