My quest is not why. That is easily understood. My question is how!
I guess I can research this but currently working on a hard landing study. Not enough time.

Thanks for the info RB.

Quote:

Why ? Why incentivize (ie remove/reduce disincentives) hard landings ? If these happen more often than can be explained by random and extreme weather, then they're being caused by poor airmanship, which isn't something to reward or ignore ... it's something that needs to be addressed before worse outcomes happen.

I don't think they're trying to incentivize hard landings; they're trying to maximize revenue, which doesn't have to preclude berating or derating pilots prone to hard landings. Based on the tone of the article, the operators already know who's doing the hard landings and whether they're bad or whatever; they want to be able to put the plane back in service as quickly as possible to generate more revenue from each airframe.

TTFN (ta ta for now)
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As to the how, my guess would be a combination of accelerometers and strain sensors, the former to detect the hard landings, independent of actual reports from the pilots and the latter to measure the consequence of the landings. Over time, they can then correlate the landing conditions to the failure points and failure rates of components.

TTFN (ta ta for now)
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the less impactful we make something, the more we are doomed to relive it.

And as for the economic argument, if you're having so many hard landings that they're impacting (no pun intended) your bottom line ... you have bigger problems.

All that said ... 2 months maintenance as a result of hard landing ?? Why ? Because the plane was scattered over several fields ?
Maybe the TAR is particularly sensitive to hard landings ? And now they're making it into a STOL plane ? we'll see how well that goes !?

another day in paradise, or is paradise one day closer ?

It looks like they are building a database from the loads measured during landing to correlate with reported damage from current inspection processes to see if there are particular landings where damage is not expected because in similar landings damage was not discovered. The time involved must be to retrieve the data from the plane.

I've been in a similar situation with a delicate piece of equipment that the customer kept banging into things. Our handling carts had guards all around, but the blue suiters for some reason did not. So the question was, is it OK if they just bend the parts back. It turned out that for small deflections that, yes, the alignment was restored well enough, but if it went farther then it needed to be returned. I figured some blue suiters were already bending them back to avoid explaining the damage, so I doubt it made much difference on the "permission" side. The allowed amount was smaller than the usually bashed them anyway. So it gave them a better barrier as it was an easy measurement to make vs "never acceptable" Now they had responsibility where before they only got blame. People generally avoid blame and most will take responsibility if it's not too much.

In terms of moral hazard, I just watched a bit from the Trailer Park Boys, where an alcoholic got a breath tester and uses it to keep his alcohol levels "just right" He knows when it's too low that he needs to top off. Fictional, but humor is often based on truth - testers in bars are sometimes prone to this abusive use.

However, I expect there are few pilots looking to see how close they can get to a landing hard enough to trigger the inspection, but not hard enough to break the plane.

For grins... FYI...

AIR1489 Aerospace Landing Gear Systems Terminology

AIR4566 Crashworthy Landing Gear Design

AIR5938 Information on Hard Landings

ARP4915 Disposition of Landing Gear Components Involved in Accidents/Incidents

ARP5600 Disposition of Damaged Wheels Involved in Accidents/Incidents

ARP6265 Tire Burst Test Methodology

and for fun...

AIR5661 Compartment Decompression Analysis

AIR5875 Methodology for Investigation of Flight Control System Anomalies

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
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I was referring to the 2 months of down time = ZERO REVENUE.

A hard landing simply means a landing that is harder than the envelope of "normal" landings, but shy of a crash. So the airplane is functional, but things might be bent or broken, such as ranging from blown tires, which are easy enough to replace, to bent struts or broken supports, which require a re-build and possible re-alignment of the damaged sections. I would assume the latter requires durations in the month range, and a loss of around $300k/day in revenue, so 2 months would be something like $18M lost revenue.

TTFN (ta ta for now)
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I guess the question is how does an airplane (a design, a design team) get to the state that a hard landing (and not a crash) gets months of downtime ?

Is the airplane that tender ?
or have we forgotten what really needs to be checked ?
or have the lawyers arrived ? "what do you mean you didn't check the flux converter ? You put my client at risk !" "yeah, but checking the flux convertor is a pain in the a$$ and is never affected by a hard landing." "how do you know if you didn't check ? Money please, thank you."

another day in paradise, or is paradise one day closer ?

The design team projects what the repeated safe landing slam is, like if you dropped the plane from 3 feet 10,000 times and it is fine sort of slam. Hard landings are those that are above that, like you only dropped the plane once from 4 feet, but not into the area where a crash response team is sent out. A big fat gray area, ripe for the picking.

It is a little ambiguous to me why it would take 2 months if there's no damage that would escape a visual inspection over a few days - it is certainly the case that 2 months to replace a bent landing gear is possible, but that doesn't seem to be what this software/system is for. If the wing is wrinkled or the fuselage is puckered at the main gear, then it should take a few minutes to say "That ain't right" and park it for repairs. But I don't know if there are planes that are partially disassembled to look deeper for bent or broken items.

I do like W K's list, but it's all paywall stuff.

One of the jobs I used to do was to take the forces measured by 6dof wheel force transducers on a durability test, and distribute them through all the components, to give a force time history for each component in the car. Then the FEA fatigue guys would do their magic.

Cheers

Greg Locock


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This reminds me of a company I worked for,
Observation from design office: Hmm the Fairchild Metros seem to be spending a lot of time in the hanger for fuel leaks in the wing tanks at the moment.
Response from hanger: Happens every time they are training a new batch of pilots on them!

SAE AIR5938 provides a fairly good understanding of 'hard landing'.

In MIL operations, hard landings occur infrequently but are taken very seriously.

Within the last few years, one of our [4 engine] jets experienced a severe hard handing [hot/gusty/desert-summer-day] that actually distorted/damage several engine pylon 'fuse pins**'. At least [3] fuse-pins were found out-of-round and showing small shear displacements at the interfaces between the [3] lugs. When I had a look at the preliminary field inspection report from a young USAF engineer [asking for my advice], it raised the hair on the back of neck and I made calls raising red-flags to the senior level.

Due to parts availability, the repair/restoration required depot fabrication of new pylon bushes, line-reaming the [undersized] bushes IDs in alignment fixtures [retrieved from storage]... and the installation of 'used' fuse-pins, salvaged-from stored/attrited Acft at AMARG. What a nightmare.

** 'fuse pins' on our jets are large diameter/hollow VHS steel pins in the strut mounting, that are precisely machined [OD/ID]... calibrated to ensure that they shear cleanly at a specified, not-to-exceed, shear-load... so the strut/engine separates in a specified/safe way/direction during crash landings or other impacts/collisions. Each lot of shear pin rough-machined heat-treated stock was destructive-tested to determine the actual shear/tensile allowables for that specific 'HEAT/LOT' of steel... and the precise ID dimension was determined from design charts [calculations] for that specific material. VERY unique parts.

xxxxxxxxxxxxxxx

V-M-M Did You, also, work for Fairchild-Swearingen [SA Tx]... or for one of the many operators of the 'Sweatro'?

Did You see the photos of the cargo Metroliner, that experienced a mid-air collision very recently?

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

Wil, I worked a relatively modest freight / charter / air ambulance operator (~20 airframes, 6 types) that only had a design office, because they could spin it off the sister company's design office (Rotorcraft Mod shop). I liked the 227's they were cheap, performed well and atleast fuel wise economical (plus they gave us plenty of interesting work). The 227 made an interesting contrast to the F27's and J32 they operated, the later two looked like they would make their design life without really breaking a sweat (90,000 cycles) if one could just get the parts. While the 227's (35,000 cycle life) were flying crack repairs even at the mid life point, they were however a good demonstration of what does/doesn't work if pushing the edges of good design i.e. steel window frame doublers might work fine but prepared for non-inspectible corrosion issues if you let the paint get a bit poor!

As for the Key lime collision, the mind boggles with the fact that it managed to keep the tail, in the ones I supported the floor track stopped at the edge of the cargo door (as did the floor panels), otherwise I would have assumed that they were what was taking much of the loads no longer passing through the ceiling.

How "very" recently? The Key Lime sundeck mod was a year ago, May 13, 2021. I think that wasn't a hard landing situation (all humor solely due to everyone surviving - whistling past the graveyard.)

Imagine if the stress guy who did the analysis looked at the rest of the team and said "I told you the floor needed to be that strong and you all said it could be lighter."

VMM... I was a SA TX factory liaison engineer at Fairchild-Swearingen for ~1.5 Years, early 1980s, until laid-off. I got to know the Merlins and Metros [SA226 & SA227] intimately, from the inside-out. Still have some liaison data. Fond memories for the birds... and friends... but that's when I encountered my first few managers-from-hell. We often learn from the good which merges into our blur of experience... but we remember the worst experiences as bright light and searing heat of what-not-to-do-ever.

Thankfully, When I was headed for lay-off, one of the senior engineers, who had worked at SA-ALC Kelly AFB AS TX... pointed out that USAF was beginning to hire new-blood aero engineers with experience... for the first time in ~7 years. I got hired fairly fast and never looked back. I've kept-in-touch with one other FS engineer all these years, who stayed in the commercial world. Interesting comparing careers after diverging from FS ~1982. DANG 40-years has gone by too-fast. We often trade info/experiences...

For those of You wondering about the 'Key Lime and Cirrus' mid-air mishap... The SA227 [cargo flight?] and a Cirrus [training flight] collided near a Colorado airport. The SA227 continued-on-to make an 'uneventful emergency landing'. The Cirrus had to use the CAPS [force deployed parachute] system to save the pilots. I always wondered how such brightly painted aircraft [lime green, obviously] could NOT have been seen by the Cirrus pilots. Oh Well... blessing of no casualties.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

HARD LANDINGS PROMPT GULFSTREAM OPERATION LIMITATIONS
FAA UPDATES 2020 AIRWORTHINESS DIRECTIVE FOLLOWING SECOND INCIDENT
https://www.aopa.org/news-and-media/all-news/2022/...

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

that seems awfully restrictive !

another day in paradise, or is paradise one day closer ?

hmmm... seems somewhat similar to 737 MAX

TTFN (ta ta for now)
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