Flap retraction during landing roll

caliginousface said:
the dutchess and i'm sure other aircraft don't have squat switches, but they rely on a certain airspeed to determine if the motor will cycle the gear selection.
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All the complex Piper aircraft that I have flown have squat switches to prevent inadvertant retraction. I find that really hard to believe that the Dutchess (basically the same thing as a Seminole) doesnt employ the same method.
 
CapnJim said:
B767's post is excellent.

I'm split, so here's my General Rule of Thumb: If the plane has a gear lever, don't fiddle with flaps on the runway. If it dosen't put 'em up, if you want.

Here's a related side-note story about squat switches:
I remember this girl on her commercial checkride at my old field. She was in a Cutlass, a 172RG. End of the chekride, everything good so far, all that was left was a soft field demonstration. She floats in and squeaks it on, nose high in the air-- perfect. Then she went to put the flaps up.
Now, at this point I should tell you that the Cutlass landing gear squat switch is located on the nose wheel, and that the gear lever is located perilously close to the flap lever, but that would wreck the story, wouldn't it?
"Too late! Too Late!" will be the cry, when the Flatulent Man passes you by!
The Cutlass's complex gear system, whose perfectly functioning squat switch was unfortunately still high above the runway, obligingly folded the mains aft and up, the nose pulled into its well, and the Cutlass settled onto its belly, stopping the engine and prop on the runway surface after less than 2 1/2 turns. Poor girl. Poor Cutlass.

On the other side of the coin, I've won many a landing contest in a plain-vanilla 172 by flipping the flap lever up just after touchdown. Also keeps things a bit more stable on the ground in gusty and cross-windy conditions. Useful stuff in spring at a place like F50, if you've ever been there.

So my opinion is, like lots of other things in aviation, there's not always hard and fast rules. That's no fun anyway. Better to use knowledge, experience, and good judgment.
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That's a heckuva story. Good post, good advice, Jim.
 
Foxcow said:
All the complex Piper aircraft that I have flown have squat switches to prevent inadvertant retraction. I find that really hard to believe that the Dutchess (basically the same thing as a Seminole) doesnt employ the same method.
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It's interesting that I have about 150 hours in the Duchess and I still had to go dig out my Pilot's Information Manual to convince myself that he is correct (granted it's been quite a few years since I flew one), because my first reaction was "there has to be squat switches".

Sure enough, Section VII, Systems Descriptions, Landing Gear System:

SAFETY RETRACTION SWITCH

To prevent inadvertent retraction of the landing gear on the ground, a safety pressure switch is installed in the pitot system to deactivate the hydraulic pressure pump circuit when the impact air pressure is below 59 to 63 knots.
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I (re)learned something new today.
 
Our Seminoles all had squat switches. All a quarter of a century old and covered in grease, oil, and god-knows-what-else too. Didn't trust 'em as far as we could kick 'em.

Thanks, B767!
 
Minnesota_Flyer said:
Well, in a touch & go, you have a good reason to bring the flaps up while moving. On most full stop landings, there simply isn't any good reason to be messing around with the flaps while the aircraft is rolling.

Also, the real trouble comes when you move up to retractable gear aircraft. The danger of accidentally grabbing the gear lever is real, and happens all too often. I've yet to fly someplace that allows touch & gos in a complex a/c for this reason.

MF
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At Riddle we would have an exchange between the CFI and student during touch and go ops (regardless of aircraft):

Student (as they reach for the flaps during touch and go t/o roll)- "Identify"

CFI (ensures student has hand on correct lever)- "Verified"


In the end, I think there is an advantage to be had for certain aircraft in raising flaps during landing roll. As I stated in my previous post, I've had situations where I felt it was necessary. Different airplanes will call for different procedures. The more knowledgeable about your airplane you are, the better pilot you can be. The key is to KNOW that specific airplane.

Big grey area here for sure, but a great discussion we got going.

-ColM
 
GatorFC said:
The only complex plane I've flown is the Duchess so maybe I'm missing something here, but why was he pulling props back @ 200 AGL (especially the amount he was intending to going by how far he pulled out the mixture)? :insane:
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Rotate...Positive rate...gear up...power green/props green. He was in a hurry he knew how far back the props needed to go and pulled them there....it just happened he had his hand on the mixture controls instead of the prop.
 
I can't believe this is still around, well actually I can, it's in a FAA book. Remember guys, the people who wrote these FAA books are human too. Just because it is written, does not make it so, common sense folks, common sense. If you are doing touch and goes, land with 25 degrees of flaps and leave them alone on the take off. Taking off with carb heat on is fine (touch and goes), you are not going to suck up any dirt and hurt the engine. The small power loss from having the carb heat on is not going to hurt you. Flying is simply risk management. Reduce the risk to an acceptable level (thank you SIEW!) and do not add things that increase the risk factor.

Now the important question. If you are landing on a strip that is so short, that flap retraction on landing is necessary to stop in the available space, how are you going to get the airplane out of there? 99 out of a 100 times, you can land much shorter than you can take off in.
 
Dugie8 said:
If you are landing on a strip that is so short, that flap retraction on landing is necessary to stop in the available space, how are you going to get the airplane out of there? 99 out of a 100 times, you can land much shorter than you can take off in.
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Aroo? Let me use the 172 as an example because it's what I primarily fly nowadays... Really, you can't land that thing until about 100 feet down the runway (do you want to put it right at the beginning of the pavement?), whereas for the takeoff, I can actually move it to inch 1 of pavement for a takeoff. I've noticed historically (from students and my own landings) that it takes a minimum of 700 feet to land (+100 feet of safety buffer), but on a short field takeoff, I can get the plane off in around 500 feet (in the winter). So if I was dumb enough to try and go into a 700 foot runway, I'd have no problem getting out of there :)
 
Chris_Ford said:
Aroo? Let me use the 172 as an example because it's what I primarily fly nowadays... Really, you can't land that thing until about 100 feet down the runway (do you want to put it right at the beginning of the pavement?), whereas for the takeoff, I can actually move it to inch 1 of pavement for a takeoff. I've noticed historically (from students and my own landings) that it takes a minimum of 700 feet to land (+100 feet of safety buffer), but on a short field takeoff, I can get the plane off in around 500 feet (in the winter). So if I was dumb enough to try and go into a 700 foot runway, I'd have no problem getting out of there :)
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I wish I had a 172 POH here. I do have a 152 POH, and it shows longer takeoff distances than landing throughout the chart.

I'll use the coldest, lowest pressure altitude figures in the charts since that will give you the very best possible take-off performance in relationship to landing performance. As conditions get warmer or higher take-off numbers increase at a much greater rate than landing.

At 0 degrees C., sea level, the '78 152 can land (book values) with a 450 ft. ground roll, 1,160 feet req'd to land over a 50 ft. obstacle. Take-off distance is 640 ft. ground roll, 1,190 feet to clear a 50 ft. obstacle.

The numbers change drastically as temps or P.A. goes up. For example the distances at 20 C, 3000' P.A are landing in 1000' & 1870', and take-off in 540' and 1305'.

I'd be interested to see if your anecdotal numbers and experience are truly reflected in the 172 POH, or if it is simply a matter of your technique(s) not fully reflecting the aircraft's capabilities to (typically) land in a shorter distance than it can take off.
 
<talking to myself mode>

:)

Interesting tidbit from AOPA Air Safety Foundation bulletin on Cessna 172 Skyhawk safety highlights:

It requires more distance to take off than to land. But how
much more? The pilot’s operating handbook (POH) states
that the takeoff distance required for a Skyhawk at 2,300
pounds, zero wind, sea level, and 59 degrees Fahrenheit is
865 feet, but it can land and roll out in only 520 feet. So it
takes about 40 percent more distance to take off than to
land. Unwary pilots have skillfully landed their airplanes
in tight quarters, only to find they didn’t have enough
room to take off again.
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Dugie8 said:
Taking off with carb heat on is fine (touch and goes), you are not going to suck up any dirt and hurt the engine. The small power loss from having the carb heat on is not going to hurt you. Flying is simply risk management. Reduce the risk to an acceptable level (thank you SIEW!) and do not add things that increase the risk factor.
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I assume you mention the dirt into the engine because of the unfiltered air now going into the engine with the carb heat on. I probably wouldn't try it on purpose, especially going out of a dirt field.

I think the emphasis on the fact that we are all human, and you have to weigh the options, is the overlying tone to this thread. Like I said before, a big grey area here, unless of course a fed is present, then in that case I'll go by what the POH recommends.

Great response to this one, I never thought it would go on this long (I think its time to end it though). Thanks to everyone who replied.

-ColM
 
And for our next topic, should you lean during ground operations?

That has been the subject of a 50 email thread from my flying club.
 
SteveC said:
I'd be interested to see if your anecdotal numbers and experience are truly reflected in the 172 POH, or if it is simply a matter of your technique(s) not fully reflecting the aircraft's capabilities to (typically) land in a shorter distance than it can take off.
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Well if it makes any difference, I am using an SP, which has so much HP it doesn't know what to do with it :) And my point was that you land X feet down the runway, which is going to artificially lengthen your runway length to land, for example:

Runway is 2000 feet long, you land 100 feet from the end of the pavement and stop in 600 feet, you've used 700 feet, whereas on the takeoff, you can go to the first inch of pavement, and if you can get off the ground in 650 feet, you've "used less runway" even though the ground roll was less...

Of course, a lot of my experience is with students doing it too, I haven't had much practice flying a "perfect" short field landing, but I'm pretty sure you could get the SP off in less room than it takes to land.
 
Chris_Ford said:
Well if it makes any difference, I am using an SP, which has so much HP it doesn't know what to do with it :) And my point was that you land X feet down the runway, which is going to artificially lengthen your runway length to land, for example:

Runway is 2000 feet long, you land 100 feet from the end of the pavement and stop in 600 feet, you've used 700 feet, whereas on the takeoff, you can go to the first inch of pavement, and if you can get off the ground in 650 feet, you've "used less runway" even though the ground roll was less...
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Thus the reason that I quoted "land/take-off over 50 ft. obstacle" distances, not just ground roll distances.

Of course, a lot of my experience is with students doing it too, I haven't had much practice flying a "perfect" short field landing, but I'm pretty sure you could get the SP off in less room than it takes to land.
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Could be. How about grabbing a POH when you have one handy and letting us know what the book says?
 
I am guilty

of rasing flaps after touchdown. At JZI we have one runway that is 5000 feet long. The only exits from the runway are at the ends. I could land ahlfway down the runway but that seems like a poor idea so I land at the 100 - 200 foot mark, retrace flaps once the airplane is stable on the pavement and then give it some gas to get down to the end of the runway and out of the way of whoever is behind me. I can taxi much faster with the flaps up and feel safer than if I had them down.

Also regarding touch and goes with carb heat and flaps down. My 69 C150 will have a tough time getting in the air at gross with flaps down and carb heat. That little 100 gerbal power out front doesn't do so well with carb heat in and those big flaps sure make a lot of drag on the takeoff roll.
 
SteveC said:
Thus the reason that I quoted "land/take-off over 50 ft. obstacle" distances, not just ground roll distances.

Could be. How about grabbing a POH when you have one handy and letting us know what the book says?
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Yeah but the 50 foot distances seem inappropriate too, since it seems like it would take less distance to go down 50 feet than come up 50 feet (in an airplane, at least)... But I will grab a POH on Thursday if I remember :)
 
Sometimes its OK

I agree with both sides of the discussion on flap retraction. One situation where it would be in the interest of safety to retract the flaps is in high wind situations in very light AC ie 150/152.

In this environment the wind speed in gusts is often close to the stall speed of the aircraft with full flaps. The safest way I've found to land a 150 in these conditions is to use 30 degrees and after the aircraft is on the ground quickly retract the flaps to get as much positive contact with the ground as possible. Of course this works best in an aircraft with manual flaps.
 
tonyw said:
And for our next topic, should you lean during ground operations?

That has been the subject of a 50 email thread from my flying club.
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Glad you asked! My answer to is, like to the flaps-on-runway question, is "It depends". Brand new plane? Probably dosen't need too much. Older bird? Prolly needs a lot more.
And guess what? To no one's great suprise, I have a story about it!

During my brief stint as a skydiver-driver, I was in charge of a C-182..... B! Yeah. I think it was vintage 1958, or thereabouts. Three different colors, no interior, clamshell door, and more MEL stickers than instruments. A true jump plane. The owner brifed me from day one that it needed to be leaned a lot, but I didn't know the extent of how much until it started sputtering on climbout-- with a full load of jumpers.

I was at about 1500 ft when the hesitation began, and I started every combination of carb heat, mixture, mag, and throttle I could think of, to no avail. I was still climbing, but barely, and had to tell the senior jumper our situation.
"Hey man, HEY!" I yelled over the motor.
"Yeah?"
"You hear all that?"
"Yeah! What the hell?"
"Dude, I dunno. We ain't goin' all the way up to twelve five, I know that much. I'll get as high as I can and let you know, OK?"
"Yeah," he giggled, "OK dude!"
I never got the chance to speak to him again. He knew as well as I did when we were at 5,500, thier minimum jump altitude, I was still dicking with the engine when the clamshell door flew open I and was very suddenly all alone. The last I saw of the jumpers was the last guy falling backwards out of the plane, grinning like the butchers dog and flipping me double birds. They were much more comfotable under modern canopies than in the belly of a sputtering monster from the 50's, so I could hardly blame them.

I foreward-slipped the plane to get the jump door back down and latched, and then began a tight descending spiral over the field to make sure I could dead-stick it if the engine gave up the ghost. It stayed running, and save for an agressive slip with full flaps to correct for an overly high approach it was a normal landing.

The engine problem was from severly fouled plugs due to my failure to lean enough on taxi and climb during the preceeding several jump runs. I was leaning it out, but not nearly enough. My concept of lean was based on relatively new 172's, and a few fuel injected 172-SP's.
 
Jim,

How did they recommend leaning during ground ops? Just pull it back a bit...or was it referenced to the tachometer or EGT gauge?

What are you recip guys doing per leaning during ground ops?
 
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