Landing on undulating surfaces
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Landing on undulating surfaces
Our local grass strip was on an uncommonly used runway today which has quite pronounced undulations (especially midway over the main runway). Landed ok but had quite a bounce on the runout just after touchdown as was in a 152 and protecting the nose gear so had a bit of back pressure. How do others generally handle such situations - do you release back pressure after the bumps and 'fly' it along the ground in an effort to stop the nosewheel bottoming out?
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Hi, On undulating ground keep as much weight off the nosewheel as possible through the control column. On short finals use full flap and pin the correct speed as well as winding in a good dollop of aft trim.
More important is the takeoff on undulating strips. Watch for the aircraft becoming airbourne too soon at too low a speed especially in gusty conditions.
Keep the column well back and be prepared to play the pitch with the undulations ie read the ground in front.
On becoming airbourne especially if the speed is near the stall check forward to reduce the AOA until you have the correct climb speed then pitch for the climb.
Pace
More important is the takeoff on undulating strips. Watch for the aircraft becoming airbourne too soon at too low a speed especially in gusty conditions.
Keep the column well back and be prepared to play the pitch with the undulations ie read the ground in front.
On becoming airbourne especially if the speed is near the stall check forward to reduce the AOA until you have the correct climb speed then pitch for the climb.
Pace
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The advice that Pace has offered is excellent.
I will add a few things;
If you have bouced, your touchdown speed was probably suffiently greater than stall speed, that the aircraft was not done flying yet. Thus, being thrown back into the air, allowed it to fly more (which you did not want). Try to land full flaps, with the stall warning sounding at touchdown. This will greatly reduce bounces in all cases, but particularly on uneven ground.
To reduce the loads imposed on the nosegear, any taxiing is best done with about 15 degrees of flaps out, and the controls held all the way back all the time. With moderate power, the nose will come well up, and greatly reduce pounding on the nose strut. This type of operation has the added benifit of keeping the prop just that much farther away from debris on the ground which could be damaging. If the nosewheel comes right off the ground while you are doing this, that is harmless, AS LONG AS YOU DO NOT BANG THE TAIL ON THE GROUND! The rudder has plenty of authority to steer you on the ground with the nosewheel light or nearly off. If the nosegear is properly serviced, you should never have occasion to bottom it out if you're being careful.
To check the nose strut servicing roughly, put one foot agaist the nosewheel, and pull downward two hand on the prop (horizontal, mags checked and off!). If doing that with all your might will bottom out the nose strut, it probably needs service. If it seems to bottom out before the forged aluminum upper and lower stop blocks contact each other, it may be that the strut has been overfilled with hydraulic fluid, and not adequately filled with gas. Have it checked. After pulling down on the prop, it should return to have about 3" of chrome showing.
While you are taxiing on the undulating ground, and with due regard for paying attention to where you are going, take a moment to focus on the relative position of the lower center edge of the windshield to the top of the glare shield. You may notice that the windshield is sliding left and right a quarter inch or so. Though the design of the Cessna is intended to allow for this, the less the better. It is this kind of motion/loads on airframe which is resisted by the cross bracing seen in the windshields for Cessna floatplanes.
Exercise caution with 152's into short grass runways, their performance can be lackluster there!
I will add a few things;
If you have bouced, your touchdown speed was probably suffiently greater than stall speed, that the aircraft was not done flying yet. Thus, being thrown back into the air, allowed it to fly more (which you did not want). Try to land full flaps, with the stall warning sounding at touchdown. This will greatly reduce bounces in all cases, but particularly on uneven ground.
To reduce the loads imposed on the nosegear, any taxiing is best done with about 15 degrees of flaps out, and the controls held all the way back all the time. With moderate power, the nose will come well up, and greatly reduce pounding on the nose strut. This type of operation has the added benifit of keeping the prop just that much farther away from debris on the ground which could be damaging. If the nosewheel comes right off the ground while you are doing this, that is harmless, AS LONG AS YOU DO NOT BANG THE TAIL ON THE GROUND! The rudder has plenty of authority to steer you on the ground with the nosewheel light or nearly off. If the nosegear is properly serviced, you should never have occasion to bottom it out if you're being careful.
To check the nose strut servicing roughly, put one foot agaist the nosewheel, and pull downward two hand on the prop (horizontal, mags checked and off!). If doing that with all your might will bottom out the nose strut, it probably needs service. If it seems to bottom out before the forged aluminum upper and lower stop blocks contact each other, it may be that the strut has been overfilled with hydraulic fluid, and not adequately filled with gas. Have it checked. After pulling down on the prop, it should return to have about 3" of chrome showing.
While you are taxiing on the undulating ground, and with due regard for paying attention to where you are going, take a moment to focus on the relative position of the lower center edge of the windshield to the top of the glare shield. You may notice that the windshield is sliding left and right a quarter inch or so. Though the design of the Cessna is intended to allow for this, the less the better. It is this kind of motion/loads on airframe which is resisted by the cross bracing seen in the windshields for Cessna floatplanes.
Exercise caution with 152's into short grass runways, their performance can be lackluster there!
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Thanks. Re:not done flying yet - that's probably valid as I don't think I heard the stall warner. To accentuate the issue it was nearly nil wind so the bump was more pronounced. I guess it emphasises the need to stall at touchdown.
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If you want to practice I suggest White Waltham..................
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I fly out of a rough, undulating and short ish (>350m) field - I've also had the front strut bottom out and it makes me cringe a little.
I just make sure I land with full flaps and, most importantly, on speed. I try not to float and "plant" it in - not a carrier landing but get the mains down. Back pressure on the stick all the way to the stop usually gets me in with just a small bounce on the mains.
With a 10kt headwind my CFI can stop before the intersection (125m), and makes it look easy. He's the man.
I just make sure I land with full flaps and, most importantly, on speed. I try not to float and "plant" it in - not a carrier landing but get the mains down. Back pressure on the stick all the way to the stop usually gets me in with just a small bounce on the mains.
With a 10kt headwind my CFI can stop before the intersection (125m), and makes it look easy. He's the man.
