Back pressure needed on takeoff & landings in a C172

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MWright

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Question for the more experienced pilots in the group.

I went up for a flight in the left seat this past weekend for the first time in over 24 years and although the instructor was impressed with what I remembered, I had one hell of a time with the take off and landings. Of the 4 we did, 3 of the landings were flat and all the take offs were like doing a vertical climb like a military jet,

Both the landings and take offs required what I felt like were way way to much back pressure on the yoke.

The take offs were like the aircraft was glued to the runway and once it lifted off it was like a high speed climb.
The landings were kind of the opposite I would pull back pull back and land on all three wheels. The 4th and final landing of the day, I pulled through what I describe as a stop in the travel and we managed to land correctly on the mains but ended up ballooning some before touching back down again.

I don't remember C172s having what i describe as a stop in the yoke travel? The three other C172's I've flown from the left seat were all smooth in their travel and I never had trouble with take offs or landings. I didn't notice this 'stop' in the preflight check either.

This organization has a second C172N that I can try, but before I go that way I wanted to post here and see if others have an idea what to look for.

Mark


PS I might just have the instructor do a TO & Landing on the next lesson so that I can watch him at the controls. (Yes my first lesson in 24 years I was at the controls fully the minute the engine started LOL)
 
Gilbert Buettner said:
It does sound suspicious. I wonder if you thought to have the instructor do a takeoff and see if that same "stop" was there? The very first thing I would do is make sure the trim is set correctly.
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Yeah I thought about that and actually added that to my statement above. Just remember C152/C172s being really smooth and 'easy' to land and take off
 
Welcome to PoA!

"Flight controls free and correct"

If it felt like it was binding or there was something that you had to pull "through", I'd squawk the plane. Maybe a turnbuckle is getting hung up on something or the cables are twisted up? Not that that ever happens.
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The only designated stops in the elevator system are at the elevator itself. If the system is incorrectly rigged, the control column will strike either the backside of the instrument panel before the up-elevator stop is reached, or the firewall before the down stop is reached. This is very common, as many mechanics pay no attention to the service manual. A misrigged trim system will also add hassles.

Was any weight and balance done before the flight? This is part of the training. If you and your instructor are big and heavy, with less than full fuel, the airplane may have been outside of the forward CG limit. That makes for heavy elevator and the other stuff you mentioned.
 
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Dan Thomas said:
The only designated stops in the elevator system are at the elevator itself. If the system is incorrectly rigged, the control column will strike either the backside of the instrument panel before the up-elevator strop is reached, or the firewall before the down stop is reached. This is very common, as many mechanics pay no attention to the service manual. A misrigged trim system will also add hassles.

Was any weight and balance done before the flight? This is part of the training. If you and your instructor are big and heavy, with less than full fuel, the airplane may have been outside of the forward CG limit. That makes for heavy elevator and the other stuff you mentioned.
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No W/B done, it was only the two of us (330pounds maybe?) with full fuel.

If it was physical stops I would get it, but as I was pulling back I felt I had to pull even harder to get the desired effect. I might have the instructor, out of fear of being charged a "ground school fee" to take a picture of the trim control wheel and see if it was incorrectly set or labeled. He charged me $30 just to look at my past log books to see what experience I had a couple weeks back. :)
 
If it was trimmed nose down, wouldn't you have to hold back pressure throughout the flight, not just for takeoff and landing?

If you fly the same plane again, while you're preflighting, pull the yoke all the way back so you can see what you're doing, and then work the trim until the tab lines up with the elevator. That should roughly correspond to T/O trim...
 
Put a 60 lb cooler in baggage compartment, that may help, and do some pull ups to get those muscles back in shape.
 
Sometimes the elevator can stick. This is more common on PA28s, but it happens on Cessnas as well. Have maintenance lubricate yoke and elevator hinges.
 
GeorgeC said:
If it was trimmed nose down, wouldn't you have to hold back pressure throughout the flight, not just for takeoff and landing?

If you fly the same plane again, while you're preflighting, pull the yoke all the way back so you can see what you're doing, and then work the trim until the tab lines up with the elevator. That should roughly correspond to T/O trim...
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Thank you for the tip. Can you clarify or point me to another reference/youtube video on this: "and then work the trim until the tab lines up with the elevator. That should roughly correspond to T/O trim..."
 
MWright said:
Can you clarify or point me to another reference/youtube video on this: "and then work the trim until the tab lines up with the elevator. That should roughly correspond to T/O trim..."
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Just look at the trim tab. If it's aligned straight with the elevator, it's about neutral, where you want it to be for takeoff. If not, move the trim wheel in whatever direction necessary until the tab is aligned straight.
 
GeorgeC said:
If you fly the same plane again, while you're preflighting, pull the yoke all the way back so you can see what you're doing, and then work the trim until the tab lines up with the elevator. That should roughly correspond to T/O trim...
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Dana said:
Just look at the trim tab. If it's aligned straight with the elevator, it's about neutral, where you want it to be for takeoff. If not, move the trim wheel in whatever direction necessary until the tab is aligned straight.
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This is what some mechanics do, and it's wrong. The service manual appropriate to the model should be consulted. For the 172, it will tell you to run the trim wheel to full nose-down position, stop blocks loose so that the chain ends are determining max travel when they hit a sprocket, and then the tab is set to its up limit as per TCDS or manual, which is typically (as for an M model) 28° up. (The down travel is 13°.) These number vary by model, and there are significant differences between the years. Anyway, the stops are then set to give 28 up and 13 down, and since the takeoff position is pretty much in the middle of the needle travel if that indicator needle is set right (as per manual, again), the trim tab will be UP from streamlined about 7° or 8° when the needle is at the takeoff position. THAT is the right place for it, on a '69-'76 172.

Never assume anything. Look it up. The OP's school airplane is most likely badly misrigged all over the place. He should, on the ground, pull the wheel all the way back and ask someone to see if the elevator is firmly against its stop back there. I'd bet it isn't. Same with down; push forward as far as possible and see it that elevator is against the down stop. Then hold the wheel firmly in about neutral and see the the helper at the tail can move the elevator freely up and down some. If so, the cables are loose, and he's losing elevator travel range that way.

A heavy nose on takeoff can also be from a flat, or nearly flat, nose oleo. The airplane's attitude is then nose-low, and the wing's AoA is so low that there is no lift helping the raise the nose. Remember that the center of lift is ahead of the main gear, and lift from the wing will lighten the weight on the nose. No lift means lots of elevator needed to get that nose up at speed.

A misrigged trim system on a 180 or 185 can get lethal. The control forces are awesome if you have to overshoot, for instance, with the trim way nose-up. It's because the wheel is moving the whole stabilizer, and if some mechanic didn't get it set right during maintenance, and the pilot gets in, sets the trim to T/O, and takes off, he could have his hands full real quick. Even smaller airplanes with the simple trim tab can get ornery if that tab is way off.
 
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Sounds definitely like a trim issue. Did all my initial training in a 172 and they are as many have said pretty docile and forgiving. In take off the trim in the ones I have flown should be set at the white bar on the trim wheel. At landing I would always turn one click at downwind when pulling the throttle back and adding first notch of flaps, and about 5 clicks on final. Also make sure your speeds are correct.
 
Dan Thomas said:
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Anyway, the stops are then set to give 28 up and 13 down, and since the takeoff position is pretty much in the middle of the needle travel if that indicator needle is set right (as per manual, again), the trim tab will be UP from streamlined about 7° or 8° when the needle is at the takeoff position. THAT is the right place for it, on a '69-'76 172.
...
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As usual, I am delighted to be corrected. Thank you for tirelessly slaying OWTs, we are all better for it.
 
Dan Thomas said:
This is what some mechanics do, and it's wrong. The service manual appropriate to the model should be consulted. For the 172, it will tell you to run the trim wheel to full nose-down position, stop blocks loose so that the chain ends are determining max travel when they hit a sprocket, and then the tab is set to its up limit as per TCDS or manual, which is typically (as for an M model) 28° up. (The down travel is 13°.) These number vary by model, and there are significant differences between the years. Anyway, the stops are then set to give 28 up and 13 down, and since the takeoff position is pretty much in the middle of the needle travel if that indicator needle is set right (as per manual, again), the trim tab will be UP from streamlined about 7° or 8° when the needle is at the takeoff position. THAT is the right place for it, on a '69-'76 172.

Never assume anything. Look it up. The OP's school airplane is most likely badly misrigged all over the place. He should, on the ground, pull the wheel all the way back and ask someone to see if the elevator is firmly against its stop back there. I'd bet it isn't. Same with down; push forward as far as possible and see it that elevator is against the down stop. Then hold the wheel firmly in about neutral and see the the helper at the tail can move the elevator freely up and down some. If so, the cables are loose, and he's losing elevator travel range that way.

A heavy nose on takeoff can also be from a flat, or nearly flat, nose oleo. The airplane's attitude is then nose-low, and the wing's AoA is so low that there is no lift helping the raise the nose. Remember that the center of lift is ahead of the main gear, and lift from the wing will lighten the weight on the nose. No lift means lots of elevator needed to get that nose up at speed.

A misrigged trim system on a 180 or 185 can get lethal. The control forces are awesome if you have to overshoot, for instance, with the trim way nose-up. It's because the wheel is moving the whole stabilizer, and if some mechanic didn't get it set right during maintenance, and the pilot gets in, sets the trim to T/O, and takes off, he could have his hands full real quick. Even smaller airplanes with the simple trim tab can get ornery if that tab is way off.
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Thank you Dan for the clarification and things to look for. I should be flying in that plane again this upcoming Sunday. No guarantees I will be able to do these checks, but if I can I will. They have a second carburetor-ed C172 that I can also sign up for should I run into the same issue.
 
douglas393 said:
Sounds definitely like a trim issue. Did all my initial training in a 172 and they are as many have said pretty docile and forgiving. In take off the trim in the ones I have flown should be set at the white bar on the trim wheel. At landing I would always turn one click at downwind when pulling the throttle back and adding first notch of flaps, and about 5 clicks on final. Also make sure your speeds are correct.
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I have a very limited amount of time in a C172 but like 50 hours in a C152 and from my very limited experience I found them to fly almost alike and never experienced what I did this past Sunday in either model before.
 
MWright said:
Thank you Dan for the clarification and things to look for. I should be flying in that plane again this upcoming Sunday. No guarantees I will be able to do these checks, but if I can I will. They have a second carburetor-ed C172 that I can also sign up for should I run into the same issue.
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What model of 172 is it?
 
douglas393 said:
At landing I would always turn one click at downwind when pulling the throttle back and adding first notch of flaps, and about 5 clicks on final. Also make sure your speeds are correct.
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Always trim to remove the pressure on the controls, not by certain numbers of clicks. That rote method might work fine during training, but it becomes a habit, and someday when you load the airplane up with people and baggage and the CG is near the aft limit, those clicks are going to be way off. On takeoff you could have the nose rising dangerously. I think the 172M's tab position being a bit up for T/O (which pushes the nose down) is designed for a middle CG or slightly aft range loading. If you use the T/O position when you're solo you'll find yourself trimming up after takeoff, which is safer than fighting the elevator to keep the airplane from stalling.
 
While the airplane may be mis-rigged and trim not set properly, others have tackled that so I'll mention a couple of technique points.

A common mistake not yet mentioned during takeoff is to forcefully rotate the airplane. On the takeoff roll, apply back pressure to the yoke, hold that pressure steady and the airplane will fly when it is ready. Don't pull hard forcing early rotation - or put differently, don't jerk the airplane into the air.

If you are landing flat, you are going too fast. This is a more common than landing too slow. In a 172, target 60 knots over the runway numbers. If you don't hear the stall horn in the flare just before the wheels touch down, you are too fast (or the stall horn is not adjusted properly).
 
Dan Thomas said:
Always trim to remove the pressure on the controls, not by certain numbers of clicks. That rote method might work fine during training, but it becomes a habit, and someday when you load the airplane up with people and baggage and the CG is near the aft limit, those clicks are going to be way off. On takeoff you could have the nose rising dangerously. I think the 172M's tab position being a bit up for T/O (which pushes the nose down) is designed for a middle CG or slightly aft range loading. If you use the T/O position when you're solo you'll find yourself trimming up after takeoff, which is safer than fighting the elevator to keep the airplane from stalling.
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Certainly a good point. I do not fly a 172tail dragged. Only did for my initial ppl training and you make a good point about trimming to relieve pressure. I am flying a 206 and before that a 182, and really do not think about how much trim I am using. Just do it where I find I need minimal elevator pressure, though on landing because I have huge tundra wheels and an extended front fork the trim is typically with extreme nose up, and even then it is not enough to prevent almost three point landings as my videos show. But then again my plane has a rightward tendency on take off and I need left rudder. Have had four mechanics and two experienced instructor check it out and the rigging seems correct.
 
Trim and trim techniques.
I've seen instructors tell students that the take-off trim position is the neutral point. Then you get students manhandling the aircraft off the runway.

If in doubt, go practice 3-4 takeoffs, gradually adding nose up trim after each one. You'll find the correct point at which the aircraft wants to rotate without a lot of elevator up effort.
 
douglas393 said:
I am flying a 206 and before that a 182, and really do not think about how much trim I am using. Just do it where I find I need minimal elevator pressure, though on landing because I have huge tundra wheels and an extended front fork the trim is typically with extreme nose up, and even then it is not enough to prevent almost three point landings as my videos show.
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The 206 is short of nose-up trim when lightly loaded. That airplane maybe should have had the trimmable stabilizer that the 180/185 used.

douglas393 said:
But then again my plane has a rightward tendency on take off and I need left rudder. Have had four mechanics and two experienced instructor check it out and the rigging seems correct.
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Even experienced instructors know nothing about control rigging if they have never done it. And too many mechanics just ad-lib it instead of studying the manuals to make sure they get it right at that time and forever after. Here's what the manual says:

1710956639197.png

And then, the rudder trim:

1710956706247.png

Now, note one very important thing: The rudder rigging MUST be done with the nosewheel locked straight ahead by its centering cam, which means that the nosewheel has to be off the ground. The nosewheel steering bungee (actually, it's the trim bungee) is part of the rudder rigging, and if it's not disconnected during rigging, then correctly adjusted and reconnected afterward, everything is off. The rudder trim system also needs rigging if you're going to solve handling problems.

Clamping the rudder pedals using a 1x4 or similar across all four pedals is also critical.
 
Before assuming that there is a rigging/mechanical issue with the aircraft, ensure you are using proper trim and approach speeds. Landing "flat" is a symptom of too fast an approach speed and not getting the nose high enough prior to landing.

My recollection is 55-60 kt approach speed with flaps, trimmed out to neutral, should allow for a short nose-high landing flare. The C172 elevator feels quite a bit heavier to me than a C152. For takeoffs, trim to the takeoff position and rotate gently at 55 kt and it should fly away and climb at 70-80 kt, trimmed out to neutral once established. With forward CG the elevator will feel heavier.
 
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