Nepal Plane Crash
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MODS : can you start a new thread with " real of fake videos" somewhere and remove all those posts that clutter the tecnical discussion here ?. Whether this video is real or not will not reveal the cause of this accident , and frankly Facebook streaming issues are not for this thread.
The video has so far given the approximate route in unavailability of FR24 map and is helpful in that sense , pilot did not by memory head to the old airport .
to bring up google earth.
you are above the old airfield with the new airfield top right
move yourself over the new airfield.
use the keys to do a 360 rotation and you will see why it was a circling approach, it doesnt leave a lot of room for 5 mile finals.
google earth is really cool for this sort of perspective.
Use this link https://earth.google.com/web/@28.201...9.58734423t,0r
to bring up google earth.
you are above the old airfield with the new airfield top right
move yourself over the new airfield.
use the keys to do a 360 rotation and you will see why it was a circling approach, it doesnt leave a lot of room for 5 mile finals.
google earth is really cool for this sort of perspective.
to bring up google earth.
you are above the old airfield with the new airfield top right
move yourself over the new airfield.
use the keys to do a 360 rotation and you will see why it was a circling approach, it doesnt leave a lot of room for 5 mile finals.
google earth is really cool for this sort of perspective.
There have been some strange crashes recently, Bangla and the Pakistan Airbus spring to mind. No one could with any certainty have predicted what the accident investigators would uncover there. In this case whilst we don't yet know what directly caused the accident, quite a number of facts are emerging. This is reported to be a tricky airport, probably what we would refer to as a Category C field, requiring special qualification. Often this involves simulator training followed by one or more landings supervised by a trainer. However in this case the airport is only a few weeks old and there is a good chance it is not yet included in the latest simulator database, nor that the trainer had necessarily flown this particular approach before. This is all informed supposition rather than fact. But the potential for the holes in the Swiss cheese to line up is there. There is no word yet who was flying. Maybe the trainer was demonstrating how he thought it should be done. Maybe the new captain was flying. In any case it is fact that the speed was allowed to decay and the aircraft departed controlled flight too low to recover. Quite why that happened will almost certainly be revealed by the investigation. With the terrain, unusual track and speed there may well have been a number of warnings going off simultaneously. Too low terrain, pull up, woop! woop! speed, speed accompanied by the stick shaker are not an unlikely combination. Sensory overload does strange things and whilst it is hard to imagine an experienced crew crashing a serviceable aircraft it cannot be excluded at this stage.
Immediate left turn taking off from old airport
The pilots of the ill-fated Yeti Air ATR72 would have had no room to stabilise straight ahead, they were obliged to maintain a circling approach. Their only option might have been to widen it a little and GA parallel to 12 of the new airport. There was no way they were mistaken about the airport at the moment of the accident, though there might •possibly• have been a temporary confusion leading up to it if aircraft had been allowed to go lower and slower than it should.
My observation as a pax on ATRs is that once flap 30 is set (numerical marking visible to pax by window) the aircraft is pushed well nose down for final part of approach, on occasion arriving over runway with some floating, and very occasionally with a bump after ballooning during the float. In my experience some of the best landings have been achieved during very strong tricky winds, where pilots become really focussed. It seems the aircraft favours a good strong headwind component for the perfect touchdown.
Pegase Driver
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Welcome to Nepal . All Domestic operations are VFR, including those of the ATRs.
Approach plates ? : The last Nepalese AIP version avail on line ( April 2022) does not have the new airport in . For the old airport ( still in ) the only approach charts avail were the holdings ( 6 DME east or west at 4000 and 4500 Ft ) and an helicoper routes /reporting points. chart , That was it. Not sure what the situation with the new airport is . I worked there and flew in/out and around VNPK myself VFR in a SEP but that was 10 years ago. Probably the easiest airport to fly in in whole Nepal as it is relatively low ( 2600ft) flat all around and there was no smog/pollution so visibility was always good, unlike Kathmadu. . Sometimes Fog because of the nearby lake in early morning . . The 3 Anapurnas are just North but far enough not to affect the airport.
Now about stabilized approaches ? not in the Nepalese environment. . large turns 1 mile out is common in other airstips in the country to avoid terrain or downdrafts.
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I'm also pretty sure that laptops exist that have all the capabilities of a smartphone, including cell reception.
I don't deny the potential for interference with plane systems, at least in theory, but isn't it illogical to single out mobile phones over other devices?
de minimus non curat lex
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To my knowledge, EMI from on board electronic devices has been found to be *detectable* in aircraft electronics, but has never been found to be the cause of an unexpected event or anomaly.
A reasonably thorough investigation of possible EMI was conducted for Quantas 72, which experienced uncommanded pitch downs. Proximity to a naval base with a high power transmitter was investigated as well as an assortment of on board devices. The detailed results, I can't find (probably in an appendix somewhere), but the accident report summarizes the results on pages 3-4. There was no finding of any anomaly resulting from EMI.
airsafe.com/plane-crash/atsb-qantas-a330-interim-report2.pdf
Over the years, cell phones radiation has been generally reduced and bands have changed with each new "generation."
A reasonably thorough investigation of possible EMI was conducted for Quantas 72, which experienced uncommanded pitch downs. Proximity to a naval base with a high power transmitter was investigated as well as an assortment of on board devices. The detailed results, I can't find (probably in an appendix somewhere), but the accident report summarizes the results on pages 3-4. There was no finding of any anomaly resulting from EMI.
airsafe.com/plane-crash/atsb-qantas-a330-interim-report2.pdf
Over the years, cell phones radiation has been generally reduced and bands have changed with each new "generation."
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I did some basic image analysis of the twitter video. I took an image of the plane from the first frame and then 2 seconds later. I used the vertical rebar coming out the the concrete pillars to superimpose the 1st frame on the 2 seconds frame. As the camera was in motion, the alignment is very close but not exact.
Then I measured the length of the fuselage and marked off that distance increments to the later frame image. I did not account for the later image being closer and that will skew things a very small amount.
As noted on my image, I calculated that the speed of the plane was around 92 knots, ground speed. I'm guessing a bank angle of less than 20 degrees and that would change the stall speed by only a few percent.
I encourage others who can enhance the images to get better results.
Images from Twitter video
Then I measured the length of the fuselage and marked off that distance increments to the later frame image. I did not account for the later image being closer and that will skew things a very small amount.
As noted on my image, I calculated that the speed of the plane was around 92 knots, ground speed. I'm guessing a bank angle of less than 20 degrees and that would change the stall speed by only a few percent.
I encourage others who can enhance the images to get better results.
Images from Twitter video
Never come across vmc (sic) other than as vis. met. conditions but that's universally rendered as VMC. The asymmetric case has always been (and is only) Vmca or Vmcg. It would make complete sense if the correct acronym was used...and none at all when it isn't! Uncapitalised 'vmc' - and missing the a or g is a meaningless acronym. Even so I've never come across the result of exceeding that limit having a name, nor ever imagined it needed one. Is this a US expression? It certainly isn't widely known in UK or European aviation.
I completely realise there have been no recorded incidents of mobile phones bringing down an aircraft, but:
Could a mobile phone have caused an erroneous reading from the AoA sensor?
Source:
https://en.wikipedia.org/wiki/Mobile_phones_on_aircraft
Could a mobile phone have caused an erroneous reading from the AoA sensor?
Source:
https://en.wikipedia.org/wiki/Mobile_phones_on_aircraft
In this case, No.
The ATR will use sensed AOA from a AOA vane to determine stall warning and stick shaker activation, but had the warning been suppressed, it still needs an approach to a stall to have occurred, so it would not be the initiating event. On the stick pusher, the system would have been inhibited at the time, which is a curious bit of interpretation of the rules if true. AOA would not have been causal.
fdr, … yes
The stick shaker comment is also very interesting. Such a change in normal operation should have been justified by a discoverable a certification deviation.
An alternative might be a misinterpretation of changes required by retrospective inflight icing requirements; advanced, re-datumed alerting.
Any ATR operators able to confirm the stick shaker operation in these circumstances.
The stick shaker comment is also very interesting. Such a change in normal operation should have been justified by a discoverable a certification deviation.
An alternative might be a misinterpretation of changes required by retrospective inflight icing requirements; advanced, re-datumed alerting.
Any ATR operators able to confirm the stick shaker operation in these circumstances.
In this event, there is no direct indication of icing being a factor, based on the video evidence, but that is not to say that the plane had encountered icing previously and was carrying a load, that would be very consistent with the event. A spectral analysis of the SPL of the video in the cabin might be interesting, the CVR spectral and the FDR should give very good indication if the wing was clean or not. If it was contaminated, particularly the tail plane, then the flight dynamics would be very close to that in the video. I doubt that is the case, but it can only be excluded by the FDR or the CVR spectral. The crew comments may be pertinent, but historically the crew are the last to be aware of the effects of ice in spite of being first to the accident scene.
JD used to do an excellent presentation on icing, including SCLD, and tail icing. The latter is a niche field that is starting to get lean on expertise remaining in the field, and the history of development is that it can bite. FENSAP-ICE is at least a tool to help teams from getting out of sorts.
refer §25.1419, App C to §25, App O to §25...
Theres a lot to unpack, especially with all the unecessary video posts.
"On the crash - the comment by B0OM is helpful. One question I would add: given how common you say the situation is, is there a risk of alarm fatigue with the stick shaker? How often in a pilot's career might they have the shaker activate? And what does the stall recovery procedure say to do with the flaps?"
I'd honestly say I don't know (or have seen or meet) an ATR pilot who is unaware the stick shaker has activated. It's a rather intense shaker and if crews are capable and trained correctly the muscle memory should take over and they will push. Regarding flap selection.......if clean the memo items call for Flap 15 if you have Flap 30 it stays there until the clean up post event.
Reagrding Vmca.......an ATR with an active shaker or pusher will go off well before Vmca is reached in a single engine situation. In fact to get the machine to perform (demo) the Vmca you have to deactivate the shaker and pusher and take it almost to the point of stalling. Apart from demonstration in a sim during training I have never witnessed a crew get even close to Vmca.
To the comments regarding tail plane ice. My understanding is the flight was conducted in VMC and there was no icing. If there was icing and it was bad enough to develop tail plane icing the crew would have encountered severe ice and therefore the SEV ICE memo items and checklist. That checklist limits flap to 15 for approach and landing which increases your approach speed significantly and then another factor is applied meaning you'll get nowhere near your stall speed (comment: no ATR crew in their right mind would do a circling approach after a severe icing event unless there was no other option anywhere).
If as someone suggested the ground speed was around 92 knots, this ATR was unbeliveably slow for a flap 30 config, let alone a flap 15 config. Conservative manoeuvring speeds for the ATR are 180 KIAS clean, 150 KIAS Flap 15 and Gear and 130 KIAS Flap 30. Minimum speed is 95 KCAS (period) and you'll only get close to this on an empty aircraft with no wind. The Yeti aircraft was pretty full, some basic math.............ATR empty weight 13800 kg (with crew), 68 pax with bags = 6800 kg so ZFW = 20600 kg (only 2400 kg away from MTOW if it was the 23000 kg variant). I don't know the fuel they had on board so lets just say they had a landing weight of 21000 kg. Below is the base performance data
VmHB 30 (Vref) = 107 kts
Correction = 1/3 headwind or all of the gust and that will give the Vapp. Most airlines use a stabilsation criteria of Vapp 0 - +10 some use 0 - +20
Vs Flap 30 and Gear down at 21000kg is approximately 87 Kcas
Vs Flap 15 and Gear UP at 21000kg is approximately 97 Kcas
As you may or may not see ATR gives crews approximately a 1.23 buffer (23%) Vref over Vs, its concievable if you have a 10 knot headwind that the Vapp will increase to 110 KIAS moving you further from stalling.
"On the crash - the comment by B0OM is helpful. One question I would add: given how common you say the situation is, is there a risk of alarm fatigue with the stick shaker? How often in a pilot's career might they have the shaker activate? And what does the stall recovery procedure say to do with the flaps?"
I'd honestly say I don't know (or have seen or meet) an ATR pilot who is unaware the stick shaker has activated. It's a rather intense shaker and if crews are capable and trained correctly the muscle memory should take over and they will push. Regarding flap selection.......if clean the memo items call for Flap 15 if you have Flap 30 it stays there until the clean up post event.
Reagrding Vmca.......an ATR with an active shaker or pusher will go off well before Vmca is reached in a single engine situation. In fact to get the machine to perform (demo) the Vmca you have to deactivate the shaker and pusher and take it almost to the point of stalling. Apart from demonstration in a sim during training I have never witnessed a crew get even close to Vmca.
To the comments regarding tail plane ice. My understanding is the flight was conducted in VMC and there was no icing. If there was icing and it was bad enough to develop tail plane icing the crew would have encountered severe ice and therefore the SEV ICE memo items and checklist. That checklist limits flap to 15 for approach and landing which increases your approach speed significantly and then another factor is applied meaning you'll get nowhere near your stall speed (comment: no ATR crew in their right mind would do a circling approach after a severe icing event unless there was no other option anywhere).
If as someone suggested the ground speed was around 92 knots, this ATR was unbeliveably slow for a flap 30 config, let alone a flap 15 config. Conservative manoeuvring speeds for the ATR are 180 KIAS clean, 150 KIAS Flap 15 and Gear and 130 KIAS Flap 30. Minimum speed is 95 KCAS (period) and you'll only get close to this on an empty aircraft with no wind. The Yeti aircraft was pretty full, some basic math.............ATR empty weight 13800 kg (with crew), 68 pax with bags = 6800 kg so ZFW = 20600 kg (only 2400 kg away from MTOW if it was the 23000 kg variant). I don't know the fuel they had on board so lets just say they had a landing weight of 21000 kg. Below is the base performance data
VmHB 30 (Vref) = 107 kts
Correction = 1/3 headwind or all of the gust and that will give the Vapp. Most airlines use a stabilsation criteria of Vapp 0 - +10 some use 0 - +20
Vs Flap 30 and Gear down at 21000kg is approximately 87 Kcas
Vs Flap 15 and Gear UP at 21000kg is approximately 97 Kcas
As you may or may not see ATR gives crews approximately a 1.23 buffer (23%) Vref over Vs, its concievable if you have a 10 knot headwind that the Vapp will increase to 110 KIAS moving you further from stalling.
Just imagine the answer it would give if the flight was directly towards the camera?
So I'd say you need to multiply your answer by 1/sin(45 degrees) to allow for the angle (guessed at 45 degrees)
which would give 92 x 1.414 = 130 knots
Also the fuselage is 1.5 times as long in the second image as the first, so the skew may not be negligible.
Last edited by netstruggler; 20th Jan 2023 at 07:29.
The actual figures were a 47 degree turn commenced at 2DME.
Last edited by pilotmike; 20th Jan 2023 at 07:55.
