| Author |
Messages |
Bob Grimstead
Unregistered
|
      
 Posted Thursday, April 2, 2009 @ 10:03 AM
Hi Folks,
Here is an extract from
A Guide to Self-Launching Sailplane Operation
By Eric Greenwell
recommended on Collin's site
'I use full “climb” power (this varies with the sailplane type) to a safe altitude (at least 400 feet above pattern altitude), retract the landing gear, and then usually reduce power by 200-300 rpm. Why don’t I retract the gear sooner? Safety. It is important the wheels be down while I am low, should there be an engine failure or other emergency requiring me to land, or in the event of a crash. By waiting to well above pattern altitude before raising it, when I have enough altitude to do the normal pre-landing checks, I am much more likely to remember to extend it. '
I personally retract my wheel rather sooner, but never before there is no longer enough of the runway left for me to land on it, and often not before the upwind threshold.
The only, very occasional, exception is at an airshow -- and then only if the crowd is really big, where I might whip up the wheel quickly.
This gives me the best possible climb rate and looks 'cool' -- although of course it will look very stupid the day my engine stops.
I wondered what other folks did?
Yours, Bob
|
Sam M.
Unregistered
|
Posted Thursday, April 2, 2009 @ 04:58 PM
I retract my gear as soon as I rotate.
|
Jorgen
Unregistered
|
Posted Thursday, April 2, 2009 @ 05:36 PM
Hi Guys,
I confess, I often retract the wheel too soon... As I wrote in my to Swedish translated flight manual: "-It is tempting to retract the wheel when you are still low, since you have to accelerate for a while after take off before you reach climb speed". However, I seem to remember reading about one (maybe more than one?) RF 4 crash in the UK where the wheel was retracted while accelerating in the ground effect. As you all know you have to shift hands on the stick, at least if your right handed, to retract the wheel. With the 4´s sensitive elevator it´s easy to get pitch-ocillations when you do. At this UK crash this happened and the propellertips struck the ground. This reduced the prop efficiency (most of the propeller´s efficiency is located at or near the tips) and the aeroplane was unable to climb over the perimeter hedge.
Bearing this in mind, I try to wait until at least 100 ft altitude but all too often I´m too impatient for that. In those cases I tend to tell myself that I need to be clean to accelerate, but to be honest I don´t think it makes that much of a difference. Good topic Bob, it´s one of these things you might get "sloppy" about but shouldn´t.
Take 5(b) just 4 fun/ Jörgen
|
Bob Grimstead
Unregistered
|
Posted Thursday, April 2, 2009 @ 08:59 PM
Hi Guys,
It is interesing that Sam says he retracts his wheel immediately he is airborne. It was the photo of his Fournier taking off with the wheel on its way up that prompted me to mention the subject.
And you are correct Jorgen. G-AVWY had to undergo a long and very expensive rebuild, using the last spare wing in Europe after the owner's son (or son-in-law) retracted its wheel immediately after getting airborne, sank down, clipped the prop tips, was unable to climb, and went through a fence, smashing its wings.
Here it is after the rebuild:
and here's a link to the accident report:
http://www.aaib.gov.uk/cms_resources/dft_avsafety_pdf_025521.pdf
When I first learned to fly airplanes with retractable landing gear, I was most emphatically taught never to retract the wheels until it was no longer possible to land on the remaining runway ahead.
I have a buddy who broke his back and is now in a wheelchair (and got badly burned), after suffering an engine failure in his airplane shortly (but not immediately) after take-off at a fly-in. He had whipped up his wheels and flaps to make an impressive departure. After the motor failed, he didn't have time to put the wheels down again, the airplane's belly hit the ground hard and his back was broken.
Why not have a quiet word with a retractable-gear instructor Sam, and see what they recommend?
Yours, Bob
|
Donald
Unregistered
|
Posted Saturday, April 4, 2009 @ 03:59 AM
Good topic. For me it kind of depends on where I am and whether I'm being 'showy'. At my home airport there's no point in being showy so I'm probably around 300 ft or so. At a friend's grass strip with everyone watching, probably way too soon, showing off that I'm the only one there with a retract. Don't think I've ever done it so close to the ground that I risk a prop strike from a retract induced wobble.
|
Skyhawk 3
Unregistered
|
Posted Saturday, April 4, 2009 @ 11:35 PM
Michael Jones formerly of the Tiger Club in the UK, said " always be surprised the engine keeps going "
I used to do "showy" for a living in the 4 and I seem to remember that the "gear up" call was always made once we were past the point of safe runway use, this clearly varied with runway length and to have your gear down at 600' at the end of a 10,000' ft runway when we were scratching for height was also not appropriate.
I now use approx 200' unless circumstances dictate otherwise.
Happy Landings!
Need any 4 spares? email me at gawek68@gmail.com
Matthew
--------------------
|
jb92563
Unregistered
|
Posted Wednesday, April 8, 2009 @ 01:01 PM
With my first retractible wheel glider I always remembered to retract the wheel at the pre landing checklist. 
I would actually retract and lower the gear to confirm the clunk indicating it was down and locked.
I was always amazed at the flatter glide with the wheel retracted and soon started the practice of retracting gear at the end of the tow.
Ray
|
Bob Grimstead
Unregistered
|
Posted Wednesday, April 8, 2009 @ 11:12 PM
Hi Guys,
Thank you very much for your input.
Something I haven't mentioned is that under one particular set of circumstances, I do retract my wheel immediately after take-off (actually at about ten feet, I don't want to sink into the ground).
That is when making a performance-limited departure from my very short (1,200 feet) Sussex farm airstrip.
In that one case alone, I judge it to be safer to minimise the drag and maximise climb performance.
Also, by the time I'm at ten feet, there is no runway left.
See: http://www.youtube.com/watch?v=L9oL-oZ7k20
and
http://www.youtube.com/watch?v=kXoUpaoQ57o
For interest, I e-mailed my local club members, and got these replies.
Hi Bob,
My training suggested to retract at 200 feet, single or multi engine.
Hi Bob
The practice that I have been taught and adopt is to retract when the upwind threshold disappears under the nose.
I (Bob) think the last guy's got it right, but think about it yourselves and when you retract, then consider what might happen if you're hit by a gust, or have an engine failure or power loss soon after take-off.
Obviously, there's no 'right' answer for all occassions; just think about whether what you do habitually is actually safe under the circumstances of today's take-off.
Yours, Bob
[Edit by Bob Grimstead on Wednesday, April 8, 2009 @ 11:27 PM]
|
Jorgen
Unregistered
|
Posted Saturday, April 11, 2009 @ 01:48 PM
Hi Guys,
there is (at least) one more thing worth to mention on this subject. In the accident report link Bob provided there is mention of a map that interferred with the wheel retract-stick movement that caused the crash.
Keeping the cockpit "tidy" is something I often neglect myself. Sometimes the cellphone can come in handy in-flight (see "Springtimezeroniner"-thread) and answering it "in-flight" is the only time I can get away with shouting at my wife. But an ill-placed cellphone, map, camera or water bottle can make odd things happen quickly. Also, the side pockets on pants/shorts that I love to stuff with things can make it very difficult to retract the wheel, pop the airbrakes- or worse still- get them in again. If you´ve forgotten to empty your pockets (which I often do) then you might have to wrestle a bit to get things done. Wrestling with various levers in a tight "strap-on" aeroplane like the RF 4 is best done at a distance from planet Earth, as has been covered quite extensively in the "Aerobatics"- section.
In the "Modifications- Baggage compartment restraint"-post Bob offers a good solution on where to empty your pockets pre-flight. Now if I could only get one done myself...
Take 5(b) just 4 fun/ Jörgen
[Edit by Jorgen on Saturday, April 11, 2009 @ 04:03 PM]
|
Mike-RM
Unregistered
|
Posted Saturday, April 11, 2009 @ 05:50 PM
Bob will probably remember that Sportair training was not to retract the wheel below 500 feet, maybe a little conservative but good basic teaching. These days I normally pull it up at about 300 feet, like Bob, unless I need all the rate of climb I can get. As we all know, retraction requires a lot of pulling knobs and levers and requires swapping hands on the stick - not something to do close to the runway, as the comment about G-AVWY testifies. The reason we pulled the gear up immediately after liftoff on jet fighters was because we'd exceed max retraction speed in seconds, not because it looks cool (well it does but there's a good excuss for doing it!).
Mike
[Edit by Mike-RM on Saturday, April 11, 2009 @ 05:51 PM]
|
|
