Flap retraction during landing roll

B7, if you looked up 'unscentific' in the dictionary, you would be likely find their procedure.
The technique I finally settled on that would keep everyone happy was to to lean it till the engine complained, then scooch it back in till it was just barely normal.
 
CapnJim said:
B7, if you looked up 'unscentific' in the dictionary, you would be likely find their procedure.
The technique I finally settled on that would keep everyone happy was to to lean it till the engine complained, then scooch it back in till it was just barely normal.
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I teach my students to lean it out a bit (about 1-2"), enough to make a difference, but not too much so it dies on me. We are at sea level, and if we tried the above procedure at idle, whenever the throttle was increased, the engine would sputter or almost die because of the extra demand on it but not enough gas. Hard to teach students a specific procedure or method that sticks, even harder for them to remember on their own!

It has come to a point where my students have a better feel for how to clean out plugs during the runup then how far to lean the mixture during ground ops. In those cases, we obviously did not lean it enough, but with the temp. and pressure differences everyday, I emphasize that any little bit helps.

-ColM
 
unfortunately i dont have time to get into this too much right now but i just wanted to say that i disagree 100% with what dugie said about taking off with flaps in the landing position and leaving carbheat on. it can make a huge difference. i havent read the article in a while but take a look at mike d's aviation safety forum under "to land or not to land". its a very good read.
later
 
I flew tonight and I got to see just how much you can lean the plane during ground ops. I had the throttle in position for about 1000 RPM and the mix was even with it, and the engine was running fine.
 
I fly a 172SP every day, and I assure you, Chris, that you can get the thing down right at the beginning of the pavement, and get it stopped in less than 500 feet.

Ask any of my students!

;)
 
But why put it down on the first inch of pavement anyway? I mean, I don't know many 600 foot runways where it'd make a difference. I'm talking "normal, safe operations" with your "average joe" pilot (not super Lloyd, or even one-step-above-mediocre Chris :) )
 
Because perhaps you're landing in a real-world situation on a short runway!

We're not talking about training at an airport with thousands of feet of runway. We're talking real-world operations.

When I was flying the 206 in The Bahamas, I had to land (and take off the next morning) on an 1100 foot runway. Very short, very narrow, a little bit of debris, and VERY HEAVY. Do you think I wanted to give up 100 feet of runway? HECK NO!! I wanted every bit of runway I could use! So, that meant pretty much setting it down at the threshold.

And I'm barely super pilot!! ;)
 
SkyWChris said:
Don't touch nutin' until you can actually pay attention to what your manipulating.
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Second that.

"Flaps identified"

"Verified"

"Flaps retracted"

Sure its dorky, but it serves a dual purpose: 1) you don't flip the wrong lever while you're trying to make the turnoff, 2) it proves you're a blithering idiot if you still manage to make the landing gear horn go off.
 
My thoughts on the issue...

are not worth much. But:

Retracting the flaps during the landing roll does indeed help stop the aircraft in a shorter distance then aerodynamic and normal braking does during a normal landing. Hence, most manufacturers recommend retracting flaps during the landing roll for a short field landing. The FAA can not frown on this situation because it is recommended in the POH that they approved! Try doing a short field landing in a 20-30 kt crosswind and tell me that retracting the flaps didn't help with stopping distance and directional control.

Now, we have all heard of the Bonanza horror stories of the gear came up instead of the flaps... It is a logical argument because depending on the year and model of the Bonanza, the gear and flap levers are in the same exact places, just switched around (i.e. the gear lever on "Bonanza X" is now exactly where the flap lever was on "Bonanza Y" and vice versa). So be careful with those Doctor Killers :).

Also, you don't see most jets doing this procedure because the wings stop creating lift on touchdown due to GLD's (Ground Lift Dumping devices). GLD's are the spoilers on top of the wings that pop out upon touchdown. They either come out automatically, or they are manually pulled by the pilot (hmmm...does the FAA frown on that configuration change on the roll out???) That is why you rarely see airliners bounce, the GLD's kill the lift as soon as they get the Weight on Wheels signal. (I have seen a CRJ 700 bounce, the GLD's on that airplane won't deploy until you have WonW AND the thrust levers at idle...i guess that pilot didn't touch down at idle and he bounced like a...bouncing thingy..).

So I guess there is something to be said for having all the weight on your wheels to help decrease stopping distance. Light piston airplanes suggest doing it in the POH's for short field landings, and most modern jets do it automatically to get the weight on the wheels. When I fly small aircraft that has a procedure calling for the retraction of flaps on a short field...i say do it if you need it...its called "flying the plane". If you don't need to retract them, don't do it...its called "flying the plane".

Whew...rant over :) As for leaning on the ground...if it keeps your plugs clean you should do it.
 
hattrick said:
unfortunately i dont have time to get into this too much right now but i just wanted to say that i disagree 100% with what dugie said about taking off with flaps in the landing position and leaving carbheat on. it can make a huge difference. i havent read the article in a while but take a look at mike d's aviation safety forum under "to land or not to land". its a very good read.
later
Click to expand...

Taking off with flaps is a bad idea? I dont get it?? I never said landing flaps, I said 25 degrees, approach flaps on the PA28s. Come on guys, you gotta read what is said.
 
CAVOK said:
are not worth much. But:

Retracting the flaps during the landing roll does indeed help stop the aircraft in a shorter distance then aerodynamic and normal braking does during a normal landing. Hence, most manufacturers recommend retracting flaps during the landing roll for a short field landing. The FAA can not frown on this situation because it is recommended in the POH that they approved! Try doing a short field landing in a 20-30 kt crosswind and tell me that retracting the flaps didn't help with stopping distance and directional control.

Now, we have all heard of the Bonanza horror stories of the gear came up instead of the flaps... It is a logical argument because depending on the year and model of the Bonanza, the gear and flap levers are in the same exact places, just switched around (i.e. the gear lever on "Bonanza X" is now exactly where the flap lever was on "Bonanza Y" and vice versa). So be careful with those Doctor Killers :).

Also, you don't see most jets doing this procedure because the wings stop creating lift on touchdown due to GLD's (Ground Lift Dumping devices). GLD's are the spoilers on top of the wings that pop out upon touchdown. They either come out automatically, or they are manually pulled by the pilot (hmmm...does the FAA frown on that configuration change on the roll out???) That is why you rarely see airliners bounce, the GLD's kill the lift as soon as they get the Weight on Wheels signal. (I have seen a CRJ 700 bounce, the GLD's on that airplane won't deploy until you have WonW AND the thrust levers at idle...i guess that pilot didn't touch down at idle and he bounced like a...bouncing thingy..).

So I guess there is something to be said for having all the weight on your wheels to help decrease stopping distance. Light piston airplanes suggest doing it in the POH's for short field landings, and most modern jets do it automatically to get the weight on the wheels. When I fly small aircraft that has a procedure calling for the retraction of flaps on a short field...i say do it if you need it...its called "flying the plane". If you don't need to retract them, don't do it...its called "flying the plane".

Whew...rant over :) As for leaning on the ground...if it keeps your plugs clean you should do it.
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You bring up a great point about larger airplanes and spoilers. But I pose this question. IF, retracting the flaps is so beneficial to stopping distance (something a DC8 at 258000 pounds eats a lot of) why did Douglus spend so much energy and complexity in designing the spoiler system on this airplane, when a simple groundshift input could retract the flaps?

I don't know of too many airplanes today that require the spoilers be depoloyed manually. If they fail to deploy on the DC8 the PNF grabs the lever and pulls it aft, no biggie. The key there is, the person NOT driving the airplane is making the config change, and a config change that is necessary.

You guys are making a mountain out of a mole hill. What is the difference in stall speed in a Warrior with full flaps or no flaps, 6 knots? (44 to 50) What speed are you touching down at with full flaps 55 knots or so. From touchdown to break application how fast are you going now, 48 knots? What gives you more breaking efficiency, flaps haning out like air breaks, or dropping the flaps and getting 50 more pounds of weight on the wheels?
 
Dugie8 said:
You bring up a great point about larger airplanes and spoilers. But I pose this question. IF, retracting the flaps is so beneficial to stopping distance (something a DC8 at 258000 pounds eats a lot of) why did Douglus spend so much energy and complexity in designing the spoiler system on this airplane, when a simple groundshift input could retract the flaps?
?
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Good point... I have never designed an airplane before so I can't speak from an "expert" standpoint. However, spoilers are used in many phases of flight, i.e. bank control input at slow speeds and slowing down (when they slam dunk a restriction on you :) ). Although not all the spoiler "panels" pop out for each situation, I think the system would have to be developed into the aircraft regardless. Also, extending the spoilers is a quicker way of losing lift upon touchdown than waiting 15-30 seconds for the flaps to work their way up.

As far as the non flying pilot extending the spoilers manually.... Good point, I didn't even think about that aspect.
 
CAVOK said:
Good point... I have never designed an airplane before so I can't speak from an "expert" standpoint. However, spoilers are used in many phases of flight, i.e. bank control input at slow speeds and slowing down (when they slam dunk a restriction on you :) ). Although not all the spoiler "panels" pop out for each situation, I think the system would have to be developed into the aircraft regardless. Also, extending the spoilers is a quicker way of losing lift upon touchdown than waiting 15-30 seconds for the flaps to work their way up.

As far as the non flying pilot extending the spoilers manually.... Good point, I didn't even think about that aspect.
Click to expand...

Very good points. My goal here isn't to "disprove" flap retraction, but more to point out the benefit simply does not outway the risk.

On the DC8 it takes quite a bit of roll input to get the flight spoilers to deploy, almost full 30 degrees of bank to get them to start coming up and full yoke deflection to get them up completely. Also they only activate when the gear is down and then it is only 2 per side out of 5. We cannot deploy the spoilers in flight either, instead the inboard engines can be brought into full reverse in flight (fine on the JT engines, but the CFMs tend to tear parts of the cowling and flaps off :argue: )
 
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