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the deployment of all your drag deevices should be dependent on your ability to make the runway,
dump full flaps, drop gear, prop flat pitch, 30 degree roll left.
-----Original Message-----
From: Ted Noel <tednoel@cfl.rr.com>
To: lml@lancaironline.net
Sent: Sun, Jan 31, 2010 10:58 pm
Subject: [LML] Re: Engine out gear down Issue/The procedure! This was a wake up call for me..
It may not be exact, but I've done some live simulations. In a demo flight of a IV-P we saw 1,600 fpm down at 100 kts clean with a windmilling prop. I rented a Hershey-bar wing Arrow and did the following:
3,000' AGL, crosswind over the center of the active runway
Chop to idle, dump full flaps, drop gear, prop flat pitch, 30 degree roll left.
Maintain 100 kts -> 1,600 fpm down.
270 degree turn, flare over the numbers, nice landing.
It's unusual to say the least, but it worked well in the Arrow. I'm sure one could argue that 100 kts with a 30 degree bank might lead to an accelerated stall in the IV-P, but I'm not trying to maintain altitude. I'm allowing the plane to fall in a controlled manner to the threshold.
It was actually quite fun. But be careful if there's traffic in the pattern. It's really easy to overtake them. I waved off twice due to traffic before I was able to complete the maneuver.
Ted Noel
N540TF
----- Original Message -----
Sent: Sunday, January 31, 2010 9:57 AM
Subject: [LML] Re: Engine out gear down Issue/The procedure! This was a wake up call for me..
I ran through some numbers regarding Michael's comments below. Starting with the sailplane comment, he says that slowing from 135kts to 65 in a zoom can result in a gain of 800 feet. If all the energy were converted to altitude(no drag) the gain would be 1,276 ft, so a gain of 800 ft seems reasonable for a very low-drag airframe - 2/3 of the energy can be converted to altitude. In the case mentioned of 120 kts to 75 kts the number comes out to a gain of 765 ft. How much of that is eaten up by drag? Certainly compared to the sailplane, a lot. Would the altitude gain be half? I doubt it. 1/4? Maybe, so as a guess you could count on perhaps a 200 ft altitude gain. How much do you need to flare? Depends on the descent rate. I calculated it based on 2,000 ft/min - arresting that is equivalent to an altitude gain of 34.5 ft, much lower than the 200 ft mentioned above. It would be good if someone measured the actual no-power descent rate with gear and flaps down.
In summary, the math suggests that a no-power approach speed of 120 kts should leave more than enough energy to flare. How much more? I'll bet not a lot, but still more. I don't have an answer to the question, but this is how the numbers work out. I have done a full-flap no-power descent with my ES (gear down, of course :-) at 105 kts and the descent rate was over 2,000 ft/min with a frighteningly high negative deck angle. Flaring from that condition would be interesting, to say the least. My conclusion is that Randy's warning is well founded.
I would, perhaps, disagree with the admonition that retracting flaps when on final will result in a guaranteed disaster. Certainly any change in configuration at the last second creates a high work load, but at least in my airplane, the difference in behavior between 20 degrees and 40 degrees of flaps is 90% drag. So, if one were to think he was high for the landing, added full flaps and then discovered he was now low, I see no problem with then retracting the flaps to 10 or 20 degrees. Assuming the speed were high (120?) the flaps could even be retracted all the way without problem except for the pitch change required. And then dropping the flaps during the flare is a good way to arrest the descent. I'm a little reluctant to post this last paragraph as I have no credentials (no military fighter jet experience, no instructor rating, no multi-engine jet time, and no stays in Holiday Inn Express) except for a modest understanding of the engineering principles involved.
Gary
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