I think I'm over-rotating. Thoughts?

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BocaFlyer

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BocaFlyer
Hey all,

New private pilot here (90 days since I got my certificate) and I did all of my training in 172s.

I recently joined a club that exclusively has Piper Cherokees and did a couple hours of transition training with a CFI as part of my checkout.

One thing I've noticed is the controls feel 'heavier' on takeoff. When I trained on the 172s it was just slight backpressure and rotation/liftoff were pretty much simultaneous. On the Pipers, however, I apply backpressure and the nose comes off the ground but I then feel the need to give it a bit more to kind of 'force' it off the ground -- however, at this point, my airspeed starts dropping so I pitch down to accelerate before pitching up at Vy.

This just feels wrong -- like I'm doing some sort of weird no-flap soft-field take-off.

Do the Pipers rotate and liftoff differently? Is liftoff delayed a little more on them than the Cessnas? If I just waited a few seconds, would the aircraft liftoff? I'm flying out of a field with a 3500 foot runway so I think I get a little nervous when I lift the nose and the aircraft doesn't liftoff so I force it.

Curious to hear folks thoughts on this. Thanks!
 
I think you’re trying to lift off too prematurely. Keep a little bit of back pressure on the yoke during the takeoff roll and then gradually increase as the airspeed builds and it will fly off on its own. Also, 3500ft, especially in FL, is plenty of runway, so there’s no need to be nervous.
 
How do you have your trim set for takeoff? How is the plane loaded? You by yourself with a lot of weight in the back? Empty? May need adjust trim a bit


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I think you are just trying to make the takeoff in the Cherokee look like the one in the Cessna. Different types have different visual pictures. Sometime very different. It's most noticeable in takeoff and landing. The correct initial climb and the landing attitude in a Cherokee is simply more nose-low - you can actually see the runway! - than in a Skyhawk or Skyland from the pilot seat view. It's literally the first thing I teach and look for during transitions.
 
BocaFlyer said:
Hey all,

New private pilot here (90 days since I got my certificate) and I did all of my training in 172s.

I recently joined a club that exclusively has Piper Cherokees and did a couple hours of transition training with a CFI as part of my checkout.

One thing I've noticed is the controls feel 'heavier' on takeoff. When I trained on the 172s it was just slight backpressure and rotation/liftoff were pretty much simultaneous. On the Pipers, however, I apply backpressure and the nose comes off the ground but I then feel the need to give it a bit more to kind of 'force' it off the ground -- however, at this point, my airspeed starts dropping so I pitch down to accelerate before pitching up at Vy.

This just feels wrong -- like I'm doing some sort of weird no-flap soft-field take-off.

Do the Pipers rotate and liftoff differently? Is liftoff delayed a little more on them than the Cessnas? If I just waited a few seconds, would the aircraft liftoff? I'm flying out of a field with a 3500 foot runway so I think I get a little nervous when I lift the nose and the aircraft doesn't liftoff so I force it.

Curious to hear folks thoughts on this. Thanks!
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You have two basic aerodynamic differences. The low wing / ground effect and stabilator effectiveness. It sounds to me like you are rotating to soon or forcing the plane into the air. Raise the nose at rotation speed and let it fly itself off the runway.
 
Yes!! A Cherokee lifts off (only swept-wing jets "rotate") COMPLETELY differently than a Cessna 172.

Slight back pressure in a 172 will result in a smooth lift-off. That will not happen in a Cherokee. You'll need quite more backpressure, and usually, a quick back and forth movement works best.

The first notch of flaps will also help.
 
Two suggestions:
  • If you are flying the Piper Cherokee solo or with just one passenger in the RF seat you will notice on your W&B calculations your CG it is close to the forward edge of the CG envelope. That is typical of most low wing Pipers. I always used to keep a tool box or a case of oil in the baggage compartment of my Cherokee to help move the CG back so there's less elevator force needed to lift the nosewheel (and to flare during landing)
  • As you are taking off just bring the nosewheel off the ground and hold that attitude. As it accelerates it will fly off the runway.

Unlike 172s, which any student with a couple of hours can fly, Cherokees are real airplanes with the wing in the correct location and require true piloting skills to fly. :D :goofy:
 
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kgruber said:
Yes!! A Cherokee lifts off (only swept-wing jets "rotate") COMPLETELY differently than a Cessna 172.

Slight back pressure in a 172 will result in a smooth lift-off. That will not happen in a Cherokee. You'll need quite more backpressure, and usually, a quick back and forth movement works best.

The first notch of flaps will also help.
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I was getting a rental checkout in an Arrow and the CFI told me about the 1st notch off flaps thang on a short field takeoff. Don’t start out with it, but pop it in at rotation. Worked good although I didn’t really like taking my hand off the throttle to do it.
 
A PAC-750 exhibits this in spades. In that case it’s partially because the wheels are located further aft of the CG than most planes so it won’t sit on its tail during unpowered loading.

Bottom line, different plane, different characteristics. Personally I like pulling nose wheel off early, and that requires some adjustment after liftoff more so than a Cessna.

Trim and CG will help emulate the Cessna “feel” to help you assimilate all of this. Even how the struts are serviced will contribute.

These differences are normal and not indicative on their own of poor technique.
 
It's usually me and a passenger in the RF seat and W&B is definitely at the fore edge of the envelope usually. Trim is typically set at neutral.

GRG55 said:
  • As you are taking off just bring the nosewheel off the ground and hold that attitude. As it accelerates it will fly off the runway.
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This seems to be the consensus here -- I think I'm just impatient and am forcing it into the air.

I'll take it up for a few times around the patch and see how it feels. Thanks for the feedback so far -- anyone else please feel free to chime in! :-)
 
Nothing to add that others already haven't said. The Cherokee is a bit heavier on the controls so just let it fly off the runway. You may get one main up and the other a split second later but that's just how it flies. Your wing is in the correct location so don't listen to those other guys. Its takes a highly skilled and good looking pilot to master a Cherokee, welcome to the club.
 
kgruber said:
Slight back pressure in a 172 will result in a smooth lift-off. That will not happen in a Cherokee. You'll need quite more backpressure, and usually, a quick back and forth movement works best.
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None of that matches my experience (about 90 hours in the C172 and 1,150 in the PA-28). It's just about. setting the trim right during your preflight.

If you need excessive back pressure to lift off in a C172 or PA-28 in a normal (not short/soft) takeoff, it's because you have too much nose-down trim dialed in, not because either plane flies substantially differently. If you had too much nose-up trim dialed in (NOT recommended), you'd be pushing forward instead to keep from lifting off prematurely.

I like a little nose-down trim so that the default if I drop the yoke is for the AoA to decrease slightly, but not so much down trim that I have to muscle the plane off the runway. With the right trim, I just apply gentle back pressure to elevate the nosewheel an inch or two, and then when my PA-28 reaches flying speed, it flies itself off a paved runway just like a C172 will.
 
The ones I fly rotate between 60-65 kias while the 172s rotate at 55, so you may have to wait a little longer before pulling back.
Also, like people said, 2 people in the plane and cg is close to the forward limit so more back pressure is needed.
 
One more thing on top of the 5 other one more things.....

despite the tone of the thread, absolutely none of this makes much difference in the end. As long as the stall horn isn’t going off and you aren’t wheelbarrowing, you’re fine. Different planes feel different.
 
Cessnas (C152, C172) are probably not good trainers for learning how to take off in most low-wing aircraft. A C152 will fly itself off the runway as soon as it acquires sufficient speed. On the other hand, My AA-5 or a Cherokee 140 will pretty much run off the end of the runway unless nose is raised at the right time during the takeoff roll.

The Cherokee POH pretty much tells the story: Upon reaching the appropriate speed, raise the nose slightly and let the plane fly itself off the runway, then allow the plane to accelerate in ground effect to the desired climb speed, which will require lowering the nose slightly. How much to raise the nose, and how much to lower it to accelerate in ground effect is a matter of feel and practice. If you rotate too much too early, you will slow the plane and delay takeoff. If you rotate too little, the plane may not fly off the runway soon enough. Likewise, if you do not lower the nose to accelerate after departing the runway, you may degrade climb performance.

In my AA-5, I accelerate to 60 mph during the takeoff roll, then smartly rotate the nose to about 10 degrees to get it off the ground, then the nose comes down a bit without losing positive climb to accelerate to 90 mph (Vy) and then settles in about 7-8 degrees nose up for a Vy climb at full power. Your speeds and attitudes will be slightly different, but that is the general idea.
 
If you are trimmed for takeoff in a 172 it will lift off by itself.

A Cherokee will not. It will just run off the end of the runway.
 
RyanB said:
Also, 3500ft, especially in FL, is plenty of runway, so there’s no need to be nervous.
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I agree, plenty of room. Just took the rented Cherokee out yesterday and flew the family to an airstrip in the mountains. 2300 ft runway at 2000 ft elevation and I was airborne before 1000 ft.
 
Just fly the airplane. Don’t over analyze. Pitch+Power=Performance. I have not found an airplane that doesn’t behave this way though they all all have their own personality.
 
kgruber said:
If you are trimmed for takeoff in a 172 it will lift off by itself.

A Cherokee will not. It will just run off the end of the runway.
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That seems improbable. With sufficient nose-up trim dialed in, both should lift off without additional back pressure, but then they'll be trimmed for a dangerously low airspeed/high AoA on climbout.

For safety's sake, it's better to trim a C172 or PA-28 slightly nose down, and use light back pressure to lift off.
 
David Megginson said:
That seems improbable. With sufficient nose-up trim dialed in, both should lift off without additional back pressure, but then they'll be trimmed for a dangerously low airspeed/high AoA on climbout.

For safety's sake, it's better to trim a C172 or PA-28 slightly nose down, and use light back pressure to lift off.
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I learned in the Cherokee and when the trim was set for takeoff it resulted in a perfect hands off Vy climb. Once I earned my PPL I started flying the Cessnas as well since my wife likes the high wings better. I almost immediately noticed one particular Cessna would be trimmed for much slower flight, just below Vx on climb out. Now I set that Cessna for takeoff and add 1 roll forward to get closer to Vy.
 
My first checkout in a Cherokee variant the CFI taught me to set the trim at neutral. However, the POH recommends aft of neutral. Additionally, since an aircraft leaving ground effect will experience a nose-up pitching moment, the change of control pressures is an aerodynamic phenomenon and not necessarily a sign of flawed technique.
 
In my Arrow, just me in the front nobody in the back - trim set a tad aft of N, rotate around 70 mph (ahah yeah, ASI is in MPH) and no tugging, yanking, pulling needed. Just backpressure.
 
dmspilot said:
Additionally, since an aircraft leaving ground effect will experience a nose-up pitching moment, the change of control pressures is an aerodynamic phenomenon and not necessarily a sign of flawed technique.
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I thought it was a pitch down moment leaving ground effect (which is why an inexperienced pilot will panic and pull back), but I've been compensating reflexively for whatever happens for so many years that I honestly can't say for certain.
 
Will Kumley said:
I learned in the Cherokee and when the trim was set for takeoff it resulted in a perfect hands off Vy climb. Once I earned my PPL I started flying the Cessnas as well since my wife likes the high wings better. I almost immediately noticed one particular Cessna would be trimmed for much slower flight, just below Vx on climb out. Now I set that Cessna for takeoff and add 1 roll forward to get closer to Vy.
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My technique in my PA-28 is to count the number of turns/bumps in my trim wheel from full aft to full forward when I'm checking it for travel during preflight (usually 28–30 the way I turn it), then bring it back halfway from full forward, which gives me a nice, neutral trim between Vx and Vy. That means I need a bit of back pressure to raise the nose on lift off, but very little.

I don't fully trust the wire position indicator. It's usually OK, but sometimes it gets bent or snagged. Counting turns/bumps is more reliable.
 
David Megginson said:
My technique in my PA-28 is to count the number of turns/bumps in my trim wheel from full aft to full forward when I'm checking it for travel during preflight (usually 28–30 the way I turn it), then bring it back halfway from full forward, which gives me a nice, neutral trim between Vx and Vy. That means I need a bit of back pressure to raise the nose on lift off, but very little.

I don't fully trust the wire position indicator. It's usually OK, but sometimes it gets bent or snagged. Counting turns/bumps is more reliable.
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I had the good ol window crank in my trainer. No counting bumps for me. Just visually checking the setting on the ceiling then adjusting if needed during climb out.
 
Will Kumley said:
I had the good ol window crank in my trainer. No counting bumps for me. Just visually checking the setting on the ceiling then adjusting if needed during climb out.
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In that case, count the number of turns on the crank — you'll be cranking it all the way to both ends in every preflight anyway to check freedom of travel, so why not?
 
David Megginson said:
I thought it was a pitch down moment leaving ground effect (which is why an inexperienced pilot will panic and pull back), but I've been compensating reflexively for whatever happens for so many years that I honestly can't say for certain.
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Nose up tendency leaving. Nose down entering.
 
My thought is that you were flying with the club CFI... Why not ask him? Should have chatted about that during checkout, but better late than never.
 
The PA28-140 POH specifies takeoff trim just aft of neutral (slightly nose up). I would interpret that as somewhere in the neighborhood of Vy or so, which will reduce the amount of back pressure needed to initiate takeoff, and not require extra back pressure to maintain a positive climb, or excessive forward pressure to prevent getting too slow once in ground effect. It's easier to get into trouble if excessive control forces are required to maintain proper flight attitudes near the ground. But it is certainly probably best to err on the nose down side of takeoff trim if if is not set optimally.
 
BocaFlyer said:
It's usually me and a passenger in the RF seat and W&B is definitely at the fore edge of the envelope usually. Trim is typically set at neutral.


This seems to be the consensus here -- I think I'm just impatient and am forcing it into the air.

I'll take it up for a few times around the patch and see how it feels. Thanks for the feedback so far -- anyone else please feel free to chime in! :)
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This is a good plan.

kgruber said:
Yes!! You'll need quite more backpressure, and usually, a quick back and forth movement works best.

The first notch of flaps will also help.
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Please confirm this was sarcasm.
 
While the recommendations of the POH should always be considered...

What works for me is to glance at the airspeed indicator, and as it approaches the bottom of the white arc to gently start raising the nosewheel off the ground a few inches. Or a few degrees of pitch, however you like to view it. Then hold that attitude until the mains leave the ground, probably about 2 or 3 seconds later. In general, that shouldn’t be too far off from the pitch needed for a Vy climb. The amount of pressure will vary with the aircraft and trim setting, but it’s a case of “whatever it needs”*. There may be exceptions, but I can’t think of any offhand among the nosewheel GA types I’ve flown.

*Last time I over-rotated badly was my first takeoff in my Sky Arrow. I was used to the back pressure required for a Cirrus. But once aware of how much lighter it was in pitch, it was virtually the same technique.
 
Kritchlow said:
My thought is that you were flying with the club CFI... Why not ask him? Should have chatted about that during checkout, but better late than never.
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Excellent question. I did my initial checkout in an Archer and I don't seem to remember this scenario happening. The last few times where I noticed this I was flying a Cherokee 140.

FWIW, I do plan to ask, but he's out of town at the moment.

PS, Go Sox! ;-)
 
Which Cherokee are you flying--a hersey bar or a tapered wing? Might make a difference.

Despite what others have said, my transition from training exclusively in a C152 and transitioning to a PA-28-161 (Warrior II, tapered wing) was a non-event. I use one notch of flaps on 95% of my takeoffs, set trim to neutral, and keep a bit of nose-down pressure until airspeed hits 60 kts. At that point, a bit of back pressure and she lifts off.

Have the wire trim indicator checked. As someone mentioned it often pops out of its spiral track. It's easily accessible once the cover is removed. Way easier than counting turns or bumps. I suppose you could check the trim indication by setting trim to neutral and visually checking the trim tab. However, at "neutral", I'm not sure the tab is perfectly aligned with the stabilator. I hate to say, while giving the advice to visually inspect, I've never done it myself. :-)
 
Domenick said:
Which Cherokee are you flying--a hersey bar or a tapered wing? Might make a difference.
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I've noticed this in the hershey bar style wing. But my checkout (which I don't seem to recall this phenomenon) was in one of the Archers with the tapered wing. Hmmmm.

And yea, the trim indicator is suspect.
 
I know I've experienced a Cherokee (hershey bar) just accelerate down the runway and stay on the ground well past flying speed.

Why does this happen? I suspect the weight and balance moment in the Cherokee with one passenger is further forward than in a Cessna and the trim is set to a flatter pitch, so you don't get the same AOA. Or, as someone said, the wings are close to the ground.

I'm sure this is wrong and I trust I will get multiple conflicting explanations of why.
 
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