How hard is a hard landing?

deyoung

deyoung

Line Up and Wait
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Tucson, AZ
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Chris
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How hard does a landing need to be to be a maintenance concern? I did some night practice today, and rather misjudged my height above the runway, and planted it... very firmly. Either all three wheels at once or maybe just slightly nose wheel first, and bounced quite a bit. Recovered that, and landed reasonably.

Roll out felt fine, and it felt and handled fine taxiing. I went to the FBO where there decent lights and got out to walk around and inspect things - nothing wrong that I could see, but I don't know if I would be able to tell. Taxied back out (still felt fine) and did a couple more takeoffs and landings (partly since I wasn't at my home airport and didn't want to leave it), and everything felt fine the rest of the way.

I don't think I planted it hard enough to do any harm, though I will ask my A&P to look at it just in case... but just thought I'd ask. This is a Cherokee-235. Thanks!
 
deyoung said:
... I will ask my A&P to look at it just in case... but just thought I'd ask. This is a Cherokee-235.
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Good idea, since your A&P surely has seen some damage from hard landings before and knows what to look for, like bent engine mounts and wrinkles in the bottom wing skins and firewall that you might not notice for a while, if ever.
 
dtuuri said:
Good idea, since your A&P surely has seen some damage from hard landings before and knows what to look for, like bent engine mounts and wrinkles in the bottom wing skins and firewall that you might not notice for a while, if ever.
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Good point - I will look at it again in the daylight too, but I'll definitely ask him to check it. I have a new radio for him to install anyway, so he'll be there when I can get on the calendar.

I think I borked this one because I was wearing glasses that I don't usually wear; the distance correction is minor and I don't really need it for most things, but it does seem to change the perspective picture a bit. Good thing to be aware of and get used to.
 
Had a bud that did similar based on your description.

Nose Gear Mount bent some.

You need a knowledgeable person to check things out now.

Telling the Insurance Co. 3 years later about this is not a good move.
 
Yeah, I doubt they would be inclined to pay for anything if I waited that long. Even that aside, if I stressed anything enough to make it more failure-prone in the future, I'd like to know about that ahead of time. I don't *think* it was that hard - but that's why I asked, I don't really have a sense for it.
 
When I was transitioning to my new to me old plane, I knew landings were a bit too firm when post-flight I had to clean deteriorating insulation that would fall to the floor from under the panel. My landings have either now improved, or I have no more loose insulation left (or both…).
 
deyoung said:
How hard does a landing need to be to be a maintenance concern?
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Some OEMs provide guidance under Special Inspections sections of the manual. If not you can contact Piper tech support and ask for recommendations. Then review those items to see where you are at. Unfortunately hard landing while they may seem "not bad" can result in hidden damage that could cause greater grief in the future. However, without more specifics can't really offer more.
 
Did the struts punch through the wings? Mostly kidding.

I am so glad I learned to land in a school 172 because I had few hard landings after I soloed.
You must look out farther down the runway at night.
I find my buddies arrow hard to get a smooth landing verse my 172 which floats like a butterfly on landing.

I watched them replace the lower firewall on this 172 at the flight school from hard landings.
159c09ab-b02b-421b-9fa6-e102c81cf798.jpg
 
1) Good to practice your night landings, they can get tricky if not practiced
2) Good that you're asking about the plane vs ignoring it
3) Pay your A&P the $150 or so for him to look at it and see if anything is bent. If for nothing else you'll not constantly have that in the back of your head from now until your next annual.
 
I didn't want to go searching through CAR 3, so I asked grok to do it for me. It came back and said landing gear was required to absorb minimum ~3gs or 7-10fps without damage. If you hit with 3gs, you'd know it. I suspect that even if you didn't flare at all, ground effect would've gotten you under that 4-500 fpm threshold. On top of that, the Cherokee oleo struts are very forgiving. I'm not saying don't look, but I am saying it's unlikely you did any damage. Ever seen a landing gear drop test video? They're pretty dramatic.
 
Jim K said:
I didn't want to go searching through CAR 3, so I asked grok to do it for me. It came back and said landing gear was required to absorb minimum ~3gs or 7-10fps without damage. If you hit with 3gs, you'd know it. I suspect that even if you didn't flare at all, ground effect would've gotten you under that 4-500 fpm threshold. On top of that, the Cherokee oleo struts are very forgiving. I'm not saying don't look, but I am saying it's unlikely you did any damage. Ever seen a landing gear drop test video? They're pretty dramatic.
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So your landings basically suck? :p
 
Gary Ward said:
You must look out farther down the runway at night.
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Interesting take.

I recall that frequently student’s night landings were better that their daytime landings. I think the explanation was that the landing light drew their attention closer to the plane, making it easier for them to judge height. But I can see how in a landing-light-out scenario, looking farther down the runway to take in the runway lights perspective better could be good advice. In that case I’d suggest they let the plane settle onto the runway just a little faster than normal, to avoid misjudging height and dropping it in.
 
AV8R_87 said:
Did the ELT trigger?

If not, probably ok.
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Or did the doors pop open? My brother had a Swift and a rather firm short field landing dropped both sliding windows upon touchdown. It got noisy and windy at the same time. I tried to warn him he was too slow, not my fault.
 
WDD said:
True - but the key concern is the nose gear, not so much the 3 G mains.
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Agreed, and moreso on a 235 than a warrior for example, but I still doubt he did any damage. PA28s are pretty hard to hurt.
 
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"How hard is a hard landing?" To answer the question directly ... apparently it's pretty easy. :biggrin:

Seriously, I've witnessed some pretty bouncy landings (me? nooo ...) that had no damage but as others have noted, I'd let an expert take a peek at it. But, as a Sport Pilot I don't fly at night unless there is a real pilot onboard.
 
Landed my Fly Baby hard once. Note the G-meter pegged at +4....
1760625929183.png
No damage to the airplane, surprising when you realize there's no "give" in the Fly Baby's landing gear...it's stiff, with only the tires for absorbing impact.

I ended up with a backache for several days.

Ron "Geeze!" Wanttaja
 
Some years back I dropped one in somewhat "Firmly". I apologized to my wife.
Somewhat later I made a landing so smooth that it was impossible to tell when we actually landed.

I asked my wife. How did you like that one?
She replied "I don't know I had my eyes closed."
 
Jim K said:
I didn't want to go searching through CAR 3, so I asked grok to do it for me. It came back and said landing gear was required to absorb minimum ~3gs or 7-10fps without damage. If you hit with 3gs, you'd know it. I suspect that even if you didn't flare at all, ground effect would've gotten you under that 4-500 fpm threshold. On top of that, the Cherokee oleo struts are very forgiving. I'm not saying don't look, but I am saying it's unlikely you did any damage. Ever seen a landing gear drop test video? They're pretty dramatic.
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3 gs! I feel much better now haha

Seems like I’d easily bounce up 20’

Or maybe the skipping rock is a better comparison 3GS is a 3 bouncer?
 
The Cherokee 235 is a strong airplane with a resilient gear, your mechanic will look it over . You didn’t blow any tires so you probably didn’t put to high a side load on the plane.
 
Some years ago I saw a PA28 botch a crosswind landing. Hit hard with about 20 degrees of crab angle.
Saw the tire flex and deflect on the wheel, probably close to the witdh of the wheel. I was convinced the tire would pop off the wheel or the gear leg would fail. But no, everything was fine.
 
FastEddieB said:
Interesting take.

I recall that frequently student’s night landings were better that their daytime landings. I think the explanation was that the landing light drew their attention closer to the plane, making it easier for them to judge height. But I can see how in a landing-light-out scenario, looking farther down the runway to take in the runway lights perspective better could be good advice. In that case I’d suggest they let the plane settle onto the runway just a little faster than normal, to avoid misjudging height and dropping it in.
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I’m pretty convinced that when pilots who have trouble judging height say they’re looking at the end of the runway, what they really mean is they’re using such a fixated stare that they don’t see anything.

Where I struggle is getting people to not try to look 6000 feet down the runway when the RVR is 1800.
 
“No, that wasn’t a bad landing. I set it down firmly to get the tires in contact with the ground because of the crosswind and to prevent hydroplaning.”
 
wanttaja said:
Landed my Fly Baby hard once. Note the G-meter pegged at +4....
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FWIW that's just the needle swinging freely, not an actual measure of force on the aircraft, I believe. I know when I take my g meter out of the panel and shake it lightly, readings in excess of +/- 6G are not unusual. The needles just flop around.
 
Imagine how many hard landings the typical flight school aircraft sees in a lifetime.

Aircraft are drop tested during certification. The results are one of the data points used to compute max gross weight. I think it is from 4 feet.
 
Ed Haywood said:
Imagine how many hard landings the typical flight school aircraft sees in a lifetime.
Aircraft are drop tested during certification. The results are one of the data points used to compute max gross weight. I think it is from 4 feet.
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If I'd known this 20 years ago I could have had an aviation career.
 
Hehe, the good old A330 would just start spitting out a report… snitch…

Had pretty soft and squishy standards if you ask me.
 
I did a little reading on drop tests in FAR 23.725. There is a math formula to calculate the drop height, but the range is 9 to 18 inches, with one drop at 1.5x the others.
 
Ed Haywood said:
FWIW that's just the needle swinging freely, not an actual measure of force on the aircraft, I believe.
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Spoilsport. Next you'll be telling me I didn't REALLY bail out of a spinning, burning Link Trainer....

Ron "The G-Level increases every time I tell the story" Wanttaja
 
Ed Haywood said:
FWIW that's just the needle swinging freely, not an actual measure of force on the aircraft, I believe.
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Nah, if that were the case the G meter would never be accurate.

Taps, drops and rapid stops can create quite high G-force peaks.
Get one of those apps that can show you the sensors in your phone. Have a plot of the accelerometers running, then drop the phone 12 inches on a hard surface (wood table). You'll see quite the spike.
 
If it hasn't already been said. On the Cherokee, check the main gear attach points. Those bolts take a lot of stress, and some of it from before your purchase. I'm not familiar with Cherokee annual inspections, are those checked annually? AD? Are there raised dimples in the upper wing surface over the main gear?
 
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