When To Raise Flaps After T/O?

[uwochris]

Hey guys,

Is there a specific rule of thumb to use on when you should raise flaps after using 10 degrees for takeoff?

What I do is the following:
- climb at Vx (60 kias)
- once clear of obstacle, pitch down, accelerate.
- once at Vx + 5 or greater, raise flaps, accelerate to Vy.

My instructor and the POH always say to use a "safe" airspeed... but, what is considered safe? Is VX too slow to raise flaps? Is my Vx + 5 providing a good cushion, or should I accelerate to VY prior to raising flaps.

TIA.

 

[Ralph]

Vy and a positive rate of climb before the final flap retraction per the PTS.

 

[midlifeflyer]

Try an experiment. Set yourself up for slow flight with 10º flaps at altitude. Begin a short field obstacle climb at the recommended airspeed and try removing those 10º at Vx and at Vy and see which you like better.

Remember that in many singles, those initial flaps are designed to produce more lift than drag. The corollary to that is that removing them involves a loss of lift. You may find that below Vy you sense a "sinking" feeling at the time of flap retraction that diminishes considerably when you wait for Vy

 

[enigma]

My instructor and the POH always say to use a "safe" airspeed... but, what is considered safe?

Entirely in the spirit of increasing your knowledge, ;-)

Why don't you do some research and learn constitutes a safe airspeed. Go back and think about what the white arc and green arcs on your ASI mean. Figure a minimum manuevering speed for your take off weight. Determine your stall speed for the various configurations at your normal takeoff weight.
Then decide upon a retract speed that leaves you with a comfortable speed for the next lowest (retracted I presume) flap setting.

When flying a Part25 certified jet aircraft, I don't retract/reduce any flaps/slats until I am going fast enough to manuever (go above 15 degrees of bank or pull more than 1.3G's) at the reduced flap setting. It is possible to retract the flaps/slats at slower speeds, but the bank must be limited to 15 degrees or less.

Bottom line, don't retract you flaps until your speed is sufficient to provide a safe margin above stall in the reduced/no flap configuration.

regards,
enigma

 

[WrightAvia]

while watching the new guys flying at

the skydiving place, I always noticed that they actually did look like they were losing altitude just after take off...when they retracted flaps at about 300 feet or so.

We always used 20 degrees of flaps for take off in the 182's. What I did to try and change this was to work with the guys on being more "AWARE" of their flying. Like have them watch what the other guys did on their landings and takeoffs and have a simple critique session. I also found that by simply pitching for a constant airspeed during retraction, instead of a constant attitude, that that would usually keep the plane in a constant climb. No level off or descent.

So let's say for instance you're flying off of a nice grass field in a 182 laden with jumpers, using 20 degrees of flaps.

You start your takeoff roll with the yoke in your chest, you lift off in ground effect and lower the nose for say "VX", then you get to an altitude where you want to lower the nose for "VY" or your climb speed...let's just say about 90 to 95 knots. When you get to where you're trimed out for that speed, you can let the flaps up and just keep pitching for the 90 to 95 knots. It will require a re-trim for sure. I never liked to take the flaps out below 500 feet.

 

[Rick1128]

For Part 23 aircraft, I have always taught that when you are clear of obstacles and have enough speed to safely manuver flaps up, then you retract the flaps.

In Part 25 aircraft, it is the same, except you need to read the performance charts. The one you need to look at is Second Segment climb. All the charts I have looked at show flap retraction at a minimum of 400 ft AGL to 1500 ft AGL. All your Takeoff performance in Part 25 aircraft is planned on you doing this.

 

[Timebuilder]

In a 172, I went for Vy for flap retraction speed.

In the Lear (oops, I was told not to say that last year!) I saw two methods: one was to retract the 8 degrees of takeoff flaps at V2+30 knots, and the other was to add a requirement of 400 feet AGL to the speed requirement.

 

[avbug]

Timebuilder,

The general rule is not to touch anything until 400'. Also to wait until V2 plus 30, at a minimum.

One airplane I flew saw a 50 knot increase in stall speed when the flaps came up...we didn't touch those puppies for some time after coming off the tarmac. Considering we were pushing 100-200 fpm as our maximum climb rate with the flaps down, and we both had our heads in the bubble windows looking for television antennaes, trees, powerlines, and kites, we were in no hurry to get those flaps up.

When I fly the dromader now, I drop the flaps either just prior to taking the runway, or on the roll, and I take them up with the thumb switch when the airplane feels like it's ready to go without them. I usually work them up and down a bit as needed, depending on the way the airplane feels. I also drop them when pulling in a turn, and take them back out when I roll out or if the airplane is going to be pushing the limits on a downhill run. Sort of an as-needed thing, and it's mostly by feel.

Most of the single cessna's will get off and climb a bit better with the flaps adjusted to match the full down aileron deflection on one side.

 

[Rick1128]

Timebuilder,

In the Lear, read the takeoff performance section of the AFM. Second segment climb charts are based on flaps up 1500 ft AGL. But no lower than 400 ft AGL. I have not seen any Part 25 aircraft with a 2nd segment loer than that. Remember, all your performance is based on that. While the aircraft will do much better than the book. Second segment is based on engine out.

 

[bobbysamd]

Flap retraction

In a Part 23 aircraft I would leave the flaps down until I cleared the obstacle. At that point I would pitch over to Vx or Vy as appropriate and then retract the flaps slowly.

The idea, as the others mentioned, is not to dump the lift you gained from the flaps too soon. Try it sometime at altitude. Bring up the flaps to fast and it'll feel as if the airplane is dropping out from under you until the airplane picks up airspeed.

 

[Timebuilder]

I wish I could have taken a Lear AFM with me.

Anyone have one to spare?

 

[Loafman]

Avbug, what sort of flyin' contraption were you yankin and bankin in the above scenario?