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Peruvian B733 accident, runway excursion, all gear collapsed, aircraft caught fire

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Peruvian B733 accident, runway excursion, all gear collapsed, aircraft caught fire

Old 1st Apr 2017, 04:07
  #41 (permalink)  
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Nor sure but it appears that the higher speed may also be due to a reduced flap landing. Sometimes performed due to missed approach climb gradients and higher density altitude locations.

Last edited by JammedStab; 4th Apr 2017 at 15:28.
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Old 1st Apr 2017, 08:32
  #42 (permalink)  
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That is certainly flaps 15. The go-around climb gradient could very well be the reason for the flap setting.
I always wondered how those high altitude ops worked out. My FCOM says that the max landing/takeoff altitude is 8400' for the 737. Above that, there must be a special ops book somewhere that explains it. Anyone with experience in that?
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Old 1st Apr 2017, 08:39
  #43 (permalink)  
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Could this be a factor? (from The Aviation Herald),

“According to local sources there was work in progress on theleft hand side of the runway, the right hand runway half, width 22.5 meters,was available only, however the width was declared 30 meters. No related NOTAMswere published, however.”
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Old 1st Apr 2017, 15:01
  #44 (permalink)  
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It looks like a pattern of "hard landings" for 733, 734 types. Latest occurrences:

Taban B734 at Ardabil on Mar 27th 2017, right main gear collapse on landing; video

Safi B734 at Kabul on Dec 10th 2016, hard landing causes right main gear collapse

AerCaribe B734 at Bogota on Nov 9th 2016, structural main gear failures on landing

ASL B734 at Belfast on Oct 4th 2016, partial main gear failure and burst main tyres on landing

Trigana B733 at Wamena on Sep 13th 2016, hard landing results in main gear collapse
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Old 1st Apr 2017, 15:21
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Looking at the videos it certainly looks like a RH gear collapse.

I wouldn't have said the landing was particularly hard.
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Old 1st Apr 2017, 15:55
  #46 (permalink)  
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I was down there a week ago. At 11,000 feet ground speed on landing is noticably higher and both landings and departures are regularly done downwind because of surrounding high terrain. It takes forever to stop and to get to takeoff speed.
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Old 1st Apr 2017, 16:37
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Here a video from a landing in Cusco (Peru) 10700ft according to the title with a 200. Also using flap 15 (as it seems) and full flap after spoilers up.

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Old 2nd Apr 2017, 01:30
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From the video, there is a strong vibration immediately after the spoilers come up and the weight settles onto the gear followed by the starboard main gear collapsing and the aircraft departing the runway.
There appear to be issues with the torque links on the early 737 aircraft.
From a November 1998 B773 incident that seems to be representative of the issue:

NTSB short summary:

A loss of torque on the apex nut of the shimmy damper for undetermined reason(s), which resulted in a failure of the shimmy damper, and the subsequent failure of the lower torsion link of the right main landing gear.

NTSB synopsis:

The Boeing 737-300 touched down under the control of the first officer, and the pilots felt a vibration or shimmy. The captain reported that he took control of the airplane, and stopped it on the runway. Examination disclosed that the lower torsion link on the right main landing gear had failed, and the wheels had rotated 45 degrees outboard. Metallurgical examination of the failed torsion link revealed it had failed in overstress. According to a Boeing 737 Service Letter, this had happened before and was traced to excessive play at the torsion link apex joint, which rendered the shimmy dampers ineffective. The shaft on the shimmy damper was bent about 20 degrees rearward, and the apex nut which held the upper and lower torsion links together was loose on the shaft. The damage precluded a check of the apex nut for proper torque.
Not saying that this was a cause of the Peruvian accident, but it seems to fit the pattern. Perhaps some of the engineers (both types) would like to weigh in on the subject?
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Old 2nd Apr 2017, 03:06
  #49 (permalink)  
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I think you are onto something.

Peruvian B733 at Cuzco on Oct 23rd 2015, right main gear collapse on landing


"The airport reported the aircraft suffered a maintenance problem and became disabled on the runway after a part in the landing gear fractured.
On Dec 14th 2016 the NTSB reported, that 8 seconds after touchdown vibrations were felt, the right hand landing gear collapsed later in the landing sequence. It was found in addition, that the left hand main gear had a fractured shimmy damper actuator and a fractured torsion link."
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Old 2nd Apr 2017, 08:57
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Simplified attempt to explain the NORMAL higher speed . . .

Simplified attempt to explain the NORMAL higher speed (in relation to the ground !) at high altitude.

To be able to fly, an aircraft needs to let a certain amount of air particles pass the wings, during a specific time period. So, it needs to travel at a certain speed through the air.

The density of the air at a higher altitude is less. The AIR PARTICLES are at a GREATER DISTANCE from each other. This distance increases with altitude.
In other words: When you go higher, the PATH from one AIR PARTICLE to the next will be LARGER.

If the same aircraft (as above) would fly at a higher altitude, the aircraft needs to go, in the same time period, a larger distance to be able to pass the same amount of air particles.

The number of air particles that passes, is a measure for the (Indicated) Airspeed (IAS).
The IAS is measured by the pitot tube. The pitot tube 'eats' the air particles and sends 'the amount eaten' to the pointer of the Airspeed Indicator.

At high altitude, in the same time period, the tube needs to 'eat' exactly the same amount of air particles to keep the aircraft flying as it needs at sea level. So, in reality, it needs to go faster (in relation to the ground). But the Indicated Airspeed will be the same . . .

The airport altitude is around 11.000 feet. The speed increase effect is, except for pilots doing this on a routine basis, way beyond what one would expect and quite significant.

Kind regards, learner . . .

Last edited by learner001; 4th Apr 2017 at 15:50.
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Old 2nd Apr 2017, 10:57
  #51 (permalink)  
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Assuming zero wind, groundspeed (GS) equals true airspeed (TAS), which is indicated airspeed (IAS) corrected for density error, an increase of roughly 2% for each 1000 feet above sea level. The aerodynamic properties of aircraft relate to IAS. A typical approach IAS for a B737 (Vref + 5) is in the region of 130 knots. At 11,000 feet density error will be approx 22%, so the TAS (and zero wind GS) will be approx 160 kt.

If for some reason the approach is made with Flaps 15 (rather than 30 or 40) the Vref will be increased by approx 10 kt, as will therefore TAS and GS.

(Source: 'How Airliners Fly' by Julien Evans)

Last edited by Discorde; 2nd Apr 2017 at 11:10.
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Old 2nd Apr 2017, 11:56
  #52 (permalink)  
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Thanks for the above posts. Given the altitude (and relatively high temperature?) of the airfield what would be the typical touchdown ground speed for a 733?
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Old 2nd Apr 2017, 13:06
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Looked like a good landing until the RH LNDG collapsed.
Similar accident happened a couple of years back with a 737-300 at Honiara, Guadalcanal in the Solomon Islands. Shortly after smooth touchdown the right landing gear collapsed. For logistical reasons the 737 written off.
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Old 2nd Apr 2017, 23:34
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Judging from the very dynamic landings that these high altitude landing aircraft seem to be experiencing (High Approach Speeds) it appears that the landing gear is taking more of a beating than their lower altitude operating cousins. As a result, the landing gear is going to need a higher frequency of inspections and maintenance. The Apex bolts on the landing gear scissors seem to need particular attention.

Here is a link to another incident report on the subject with a pretty explicit write up on details of the failures.

The Safety recommendations in the link worth noting.
Safety Recommendations
There have apparently been a substantial number of MLG torsion link fracture cases brought about by severe shimmying over a period of years. While none of the previous cases resulted in injury, it is clear that such events are likely to have a significant effect on the aircraft's steering capability, could inhibit use of the wheelbrakes in the event of shimmying and are likely to result in wheel, tyre and brake damage. A runway departure could possibly be the eventual result of such an event.
Additionally, it appears that the substantial oscillatory loads associated with MLG shimmy, both before and after torsion link fracture, could potentially cause undetected damage to the aircraft structure.
Changes to relevant sections of the AMM and MPD, together with a number of messages from the manufacturer emphasising the recommended maintenance, have apparently failed to prevent recurrence. It is considered that further measures, including an assessment of the need for improved methods of checking for excessive play in the torsion link apex joint and an increased check frequency, improvement to relevant sections of the AMM and assessment of the need for modification of the joint, need to be implemented. It has therefore been recommended that:
Safety Recommendation 2004-103
The Federal Aviation Authority and the Boeing Commercial Airplane Group should take effective measures aimed at preventing further cases of Boeing 737 main landing gear shimmy and resultant torsion link fracturing brought about by excessive play in the anti-torque links apex joint.
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