Hey i land normal with 140ft or 60ft and 2,5 degrees at landing (touchdown)

 

but yesterday i land with 400ft at TNCM very hard landing

 

What is in real life the maximum for the maingears befor collaps ?

 

best regards

 

Chris

It is actually measured in G load on landing, if you really crunch it, the printer will start spitting out paper with data regarding the landing.

 

Whilst not related to the NG, here's an example of the abuse that main gears can receive

 

http://avherald.com/h?article=4555bd36

Well, you can have a 400fpm descent rate over the treshhold as long as you flare correctly.

I tend to approach with a high rate of descent and then kiss the pavement gently with a nice and smooth flare. However, this only applies to fully visual approaches for me. :-)

 

Regarding the link above - 4.1 G's sound like some serious back pain! Were these guys upfront nuts?

Were these guys upfront nuts?

 

By the look of it, they should have just shoved the levers to forward stop... man. That was some crazy landing. And first contact only 140m past threshold, must have been quite low, too!

 

 

By the look of it, they should have just shoved the levers to forward stop... man. That was some crazy landing. And first contact only 140m past threshold, must have been quite low, too!

 

I mean, shouldn't they be trained to go-around as soon as they realize that the approach is crap?

That's one of the basics at flightschool - safety first!

Just an addition: Was on jumpseat of a south european airline in a MD-88 landing at LTAI years ago. The PF (was the captain) did not initiate a flare. VS over threshold was about 700fpm. I do not know, whether the ground effect slowed the vertical speed but the landing was... well hard. But the aircraft didn't bounce and the PF lowered the frontgear smoothly down.

 

I also asked a captain some time ago... he sad, that the vsi is a ivsi connected to the IRU und didn't show real values during touchdown as the showed value is 1-2seconds behind the actual value. It was on a Condor B763.

I also asked a captain some time ago... he sad, that the vsi is a ivsi connected to the IRU und didn't show real values during touchdown as the showed value is 1-2seconds behind the actual value. It was on a Condor B763.

 

That doesn't sound right. Sounds more like the opposite.

An IVSI is a regular VSI with corrections to remove the lag found in standard mechanical VSIs. The I, of course, stands for Instantaneous.

Don't have access at the moment but in part 25 of the FARs there's a specification of the maximum touch-down rate the landing gear must be able to withstand. Off the top of my head it's 10fps so 600 fpm.

Off the top of my head it's 10fps so 600 fpm.

 

Bingo.

25.473.a.2:

"With a limit descent velocity of 10 fps at the design landing weight (the maximum weight for landing conditions at maximum descent velocity)"

 

...going on to say 6 fps at the design takeoff weight.

I think SAS uses on theirs 73:s: any landing with v/s -500 f/m or grater is considered a hard landing & requires an inspection & talk with the chief pilot :t0103:

I think SAS uses on theirs 73:s: any landing with v/s -500 f/m or grater is considered a hard landing & requires an inspection & talk with the chief pilot :t0103:

 

Sounds plausible, it might even be at v/s less than -500, limit descent velocity means that if you land any harder there are no longer any guarantees about the gear not snapping right off. You can still damage the plane if you land at less than that rate, just not enough to cause the gear to fail.

Just an addition: Was on jumpseat of a south european airline in a MD-88 landing at LTAI years ago. The PF (was the captain) did not initiate a flare. VS over threshold was about 700fpm. I do not know, whether the ground effect slowed the vertical speed but the landing was... well hard. But the aircraft didn't bounce and the PF lowered the frontgear smoothly down.

 

I also asked a captain some time ago... he sad, that the vsi is a ivsi connected to the IRU und didn't show real values during touchdown as the showed value is 1-2seconds behind the actual value. It was on a Condor B763.

Ground effect probably cushioned the descent quite a lot. It wouldn't help you out anywhere near as much in FSX though.

That doesn't sound right. Sounds more like the opposite.

An IVSI is a regular VSI with corrections to remove the lag found in standard mechanical VSIs. The I, of course, stands for Instantaneous.

Yes and no. With an analogue IVSI the indicator adds a pitch rate lead term (created by a piston in a cylinder connected to the air lines) to the very slow changing static pressure changes which drive the VSI. The first "I" stands for "Inertial", not "Instantaneous". The "instantaneous" indication isn't actual vertical speed but the trend is in the right direction. The lag still exists for a dynamic reading, as during flare. Moving on to the IVSI in a 767, as that uses IRS inputs it could show truly instantaneous VS but it would be quite erratic, so it's filtered with a Vertical Speed from the ADC to smooth things out. So it still isn't instantaneous.

 

So the 763 pilot was correct that the displayed VS is not the true value, but VS with a slight lag. A traditional barometric VSI would be even slower to catch up.

The first "I" stands for "Inertial", not "Instantaneous".

 

I'm not so sure about that. The FAA Pilots Handbook of Aeronautical Knowledge, Instrument Flying Handbook, and Advisory Circulars (AC 25-7C); the patents by Allied-Signal, Honeywell and EUROCOPTER; and a couple of the operating handbooks I have access to (the CRJ and A320 from my old IDE job) all use 'instantaneous'. The inertial seems to also be used, but mostly only on forums I've seen so far. Maybe a carryover from the fact that the IRUs drive it?

 

Either way, the fact remains that the IVSI is going to be more accurate than your standard VSI.

I'm not so sure about that. The FAA Pilots Handbook of Aeronautical Knowledge, Instrument Flying Handbook, and Advisory Circulars (AC 25-7C); the patents by Allied-Signal, Honeywell and EUROCOPTER; and a couple of the operating handbooks I have access to (the CRJ and A320 from my old IDE job) all use 'instantaneous'. The inertial seems to also be used, but mostly only on forums I've seen so far. Maybe a carryover from the fact that the IRUs drive it?

 

Either way, the fact remains that the IVSI is going to be more accurate than your standard VSI.

Nothing to do with being driven by IRS's. They were called Inertial VSIs, or Inertial Lead VSIs, long before inertial reference systems came on the scene. They use the inertia of a piston (or a mechanical bobweight system) to add a pitch rate term to the VSI pointer, so as soon as you rotate nose up or nose down the pointer will move in that direction. When you stop pitching the barometric system will have caught up and driven the pointer to its steady state value.

 

You will also sometimes see them referred to as ILVSIs, but they are all the same thing. None of them are instantaneous, but I agree they are also referred to as that. I think the term Inertial is more accurate. "Instantaneous" is rather misleading, because they aren't anything of the sort, just much less laggy than a purely barometric VSI.

 

Yes, an IVSI will of course be faster than a VSI, but it will still lag You can't use it to read the VS at touchdown, for example, which is what you inferred earlier.