PPRuNe Forums

Go Back   PPRuNe Forums > Flight Deck Forums > Tech Log

Tech Log The very best in practical technical discussion on the web

Reply
 
Thread Tools Search this Thread
Old 7th Mar 2010, 21:51   #1 (permalink)
 
Join Date: Feb 2008
Location: Kristiansund in Norway
Age: 45
Posts: 21
hard landing limit ???

I belive most airlines today use 600ft/min or 2G as their hard landing limit on their aircraft.If remember correct Scandinavian use this for their entire fleet.But at what sink rates is it likely that some sort of damage will occur,like gear damage or bent stringers.In the BA038 incident, I been told that the gear would have withstand the 1300 ft/min impact if it wasn,t digging into the grass.In a A320 tailscrape landing with a sink rate of 800 ft/min the engineers fould no structural damage except for the scrape damage.There are several videos on youtube were the sink rate has to be well over 600 ft/min as for example and awful landing of a 757 at Manchester.I also asking if a Widebody like 767 or 777 will withstand higher sink rates at touchdown because of it,s longer legs than for example a 737 or MD80? Someone with more knowledge please comment.
737forever is offline  
Old 8th Mar 2010, 00:51   #2 (permalink)
 
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,601
Quote:
hard landing limit
Usually...when your upper plate falls out.
411A is offline  
Old 8th Mar 2010, 02:34   #3 (permalink)
 
Join Date: Jun 2001
Location: Fragrant Harbour
Posts: 4,218
One interesting fact is that hard landings tend to appear worse than they actually are. I back this statement up with the evidence from my company's ASRs. You see "suspected hard landing written up in tech logs, but the subsequent analysis shows that there were nowhere near the 600fpm limit. In fact most don't even exceed the 360fpm limit for the overwight case.
Dan Winterland is offline  
Old 9th Mar 2010, 14:59   #4 (permalink)
 
Join Date: Aug 2007
Location: France
Age: 69
Posts: 2
I've been retired for a while, but from memory, 600fpm is the design limit for landings at weights up to MLW as specified by the airworthiness requirements (JAR25 in Europe or FAR25 in USA). Any landing with a vertical speed in excess of 600fpm is therefore outside the certified limits and inspections are needed to check for damage. As far as I know, all fairly modern aircraft are designed to these limits and you can't assume that any make or model is more capable than another.
Life of Leisure is offline  
Old 10th Mar 2010, 19:50   #5 (permalink)
 
Join Date: Feb 2008
Location: Kristiansund in Norway
Age: 45
Posts: 21
Seems a little strange,since I heard the stories of the Boeing test pilots who demonstrated short field landings with 727.With no flare they drove it into the runway with 700ft/min touchdowns.
737forever is offline  
Old 11th Mar 2010, 12:58   #6 (permalink)
 
Join Date: Aug 2007
Location: France
Age: 69
Posts: 2
I have just checked and both FAR 25 section 25.473 and JAR 25, also section 25.473 specify that the aircraft must withstand loads due to landing at MLW at a limit descent velocity of 10 fps, i.e. 600 fpm. I have no idea whether that was the regulation limit for the 727 or whether you are correct about a test having been performed at a higher descent velocity.
Life of Leisure is offline  
Old 11th Mar 2010, 14:00   #7 (permalink)
 
Join Date: Aug 2009
Location: South of N9000'.0
Posts: 245
If you can taxi with less than TOGA thrust, you haven't landed all that hard!
PappyJ is offline  
Old 13th Mar 2010, 10:21   #8 (permalink)
 
Join Date: Jan 2010
Location: USA
Posts: 46
You can correlate RA rate into pitch rate. The limits on the A320 to demand an inspection are:

-Normal acceleration > 2.6 G in a 1 second window around impact OR
-RA rate is > 9 FPS during the same window

You have to do a severe hard landing inspection (you might have disintegrated the L/G) if

-Normal acceleration > 2.86 G in a 1 second window around impact OR
-RA rate is > 14 FPS during the same window

The only post-landing consequence of an overweight landing is these margins are reduced. If the A/C is above MLW:

-Normal acceleration > 1.7 G in a 1 second window around impact OR
-RA rate is > 6 FPS during the same window
demands a hard landing inspection and

-Normal acceleration > 2.6 G in a 1 second window around impact OR
-RA rate is > 13 FPS during the same window
is now severe hard.

On the LRs, there's two steps for the overweight limits, depending on how overweight you were.

If you can't get this data, even after pulling the FDR, you have to assume it's a severe hard landing (and fix the FDR).
catiamonkey is offline  
Old 13th Mar 2010, 15:37   #9 (permalink)
 
Join Date: Nov 2008
Location: actually in ppruneland.
Posts: 105
HI, PRUNERS

A hard landing is defined as a landing with a vertical acceleration of more than 2.6 g at the center of gravity or:
-a vertical speed (v/s) of more than 600 ft/min.

An overweight landin is defined as a landing at more tha the maximum landing weight with a vertical acceleration of more then 1.7 g at center of gravity or:
-a vertical speed (v/s) of more then 360 ft/min.

On A-320 if the aircraft has DMU/FDIMU with an enhanced load report 15, do the "inspection after hard/overweight landing for aircraft with enhanced DMU/FDIMU load repot 15".

It is responsability of the flight cr
ew to make a report if THEY THINK THERE WAS A HARD/OVERWEIGHT LANDING.

I hope this helps.

toby.

Last edited by toby320; 13th Mar 2010 at 16:15.
toby320 is offline  
Old 13th Mar 2010, 23:42   #10 (permalink)
 
Join Date: Apr 2004
Location: Planet Earth
Posts: 1,404
IGH,


That hard landing is the reason why we disabled the Auto Spoilers on the 727.
stilton is offline  
Old 14th Mar 2010, 00:37   #11 (permalink)
 
Join Date: Jun 2001
Location: Fragrant Harbour
Posts: 4,218
Recorded g is not always a reliable method of determining if a landing was hard. The impact shock through the airframe is transmitted directly to the accelerometer and this shock itself can influence the reading.
Dan Winterland is offline  
Old 14th Mar 2010, 01:41   #12 (permalink)
 
Join Date: Jan 2010
Location: USA
Posts: 46
The A320 has its own monitoring accelerometers around the CG. They're much higher rate and much less precise accelerometers than the IRUs. Hopefully somebody at the factory figured out how they correlate to hard landings before they certified the thing.

The LRs have a ~10 of them throughout the airframe for the anti-vomit system too. The 777 has something similar.
catiamonkey is offline  
Old 14th Mar 2010, 04:59   #13 (permalink)
 
Join Date: Jun 2001
Location: OZ
Posts: 786
Back in the "Good Old Days" the DC8-50, and maybe other DC8 models, had a small strip of Al clamped to the bottom of each MLG strut pointing up. Part of the engineers' turnaround check was to see if they were still straight along the strut. If bent, it was a heavy landing and an inspection required, if straight no problem.

We called them "lie detectors" and it saved any arguing the toss with the pilots.
mustafagander is offline  
Old 16th Mar 2010, 15:10   #14 (permalink)
dv8
 
Join Date: May 2001
Location: Location Location
Posts: 380
If I recall correctly from my ATR 42/72 days on walk around there was an inspection panel near the main landing gear that had a glass bubble that showed a coloured ball if a hard landing was made
dv8 is offline  
Old 18th Mar 2010, 18:56   #15 (permalink)
 
Join Date: Feb 2008
Location: Kristiansund in Norway
Age: 45
Posts: 21
A hard landing limit of 2.6 G sounds high.After reading this,I don,t belive any more that an A 320 series has a weaker airframe than the 737 Ng and Md80 series,or maybe it has something to do with the long leg,s of the bus.A 737 driver once told me that you didn,t bother with a hard landing check unless hitting over 700 ft/min so there is some variations of the information.One more thing! Is it possible to overload the aircraft if you flare to late,with a violent pitch rate even with a decent rate within the limits? I saw a video on youtube with a Zoom 767 witch probaly had the cg well in front of the mains.When flaring late,he rotated the main gear into the runway with great force.It looked like a hard landing,but were the sink rate was well inside the limits.Since I not into computers,I am not able to give you a link.
737forever is offline  
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT. The time now is 10:06.


1996-2012 The Professional Pilots Rumour Network

SEO by vBSEO 3.6.1