Posts about: "Self Proclaimed Experts" [Posts: 10 Pages: 1]

Just read a report by Richard Godfrey on the climb and descent
https://www.dropbox.com/scl/fi/a9hhz...ioijg&e=1&dl=0
Not knowledgeable to know about a lot of this myself but interested in views. His calculation asserts that it was not a dual engine flameout to cover the distance it did but there must have been at least some thrust provided to do so.

Someone Somewhere Re your Loose rivets quote. We seem to be talking about opposite ends of the flight.

Chiefttp , Richard Godfrey is a person of interest to people with minds like the late Richard Feynman. I'm at a loss to understand how he comes to some of his conclusions, though his past work has shown streaks of genius. Reading through benjyyy 's link leaves me uneasy about the ratio of assumptions vs facts.

Disclaimer: I'm not a pilot, only a non-aviation engineer, and so I'm a bit hesitant to criticise this. And yet:

The determination of the height AGL seems quite incorrect - it completely ignores the local pressure and temperature, which very much need to be corrected for. Applying those corrections even using rough rules of thumb (~30 ft per mbar, ~4 feet per \xb0C per 1000 ft) gives a figure that's around ~100 feet AGL. The follow-up sanity check also fails even without knowing the correct math because if you match the ADS-B data (timestamp + location) to when & where the aircraft lifts off and starts to climb in the CCTV video (versus just assuming that the peak height seen in the video matches the last ADS-B data point), the aircraft is very much not 300 feet above the ground when its transponder reports an altitude of 625 feet.

Also the estimation of the glide ratio with flaps 5, gear and the RAT deployed being 3.5 to 1 seemed incredibly low to me, but I'm the first to admit that I have nowhere near as much knowledge of gliding performance as I do of weather math. So I looked up the closest incident I could think of: Air Transat 236, an A330-200 (so of a pretty similar shape, wingspan and wing area as a 787). According to the final report (link: https://www.fss.aero/accident-report...1-08-24-PT.pdf ), the aircraft arrived at a fix approximately 8 nautical miles (48609 ft) from the runway at an altitude of approximately 13000 ft, at which point the crew decided to execute a 360 turn to lose altitude as well as to extend the slats and landing gear during the turn (the RAT of course had already long been deployed at this point), both to prepare for landing and to help further lose altitude. Sure there's some rounding here, and my understanding is that "flaps 1" on Airbus aircraft deploys only leading edge and not trailing edge devices, but this already suggests that their expected glide ratio was significantly higher than the raw 48609:13000 ratio (~3.74:1).

They re-established themselves on final in their landing configuration at an altitude of ~8000 feet and a distance of 9 nautical miles (54685 ft), so let's say that the true distance was somewhere between 8 NM and 9 NM to account for rounding. That gives a glide ratio of between ~6:1 and ~6.83:1. But on top of that, the crew still had to execute a series of S-turns to lose enough altitude to actually make the runway, so their "dirty" glide ratio must have been even higher than that. Unfortunately I don't think it's possible to determine conclusively what the ratio was since we don't know how many track miles were added on by the turns (the flight data recorder stopped when the engines flamed out and human testimony only goes so far), and again they did not have flaps extended, but I think it's fair to say that a glide ratio of 3.5:1 is a wildly low estimate for an airliner of the 787's calibre even with the gear down.

Sorry if this is off-topic or too much rambling, but considering how much speculation there tends to be both in this thread and elsewhere about real-world glide performance (especially in non-ideal configurations), hopefully these details are helpful.

I think there is mileage in Richard Godfrey's reasoning, and worth listening to. Here is the latest "Airline News by Geoffrey Thomas" from 6 hours ago.


Admin note: Mr Thomas is a thoroughly debunked Australian whose aviation experience was decades ago as a baggage handler. His narrative should be taken with a mug full of salt.

We are leaving this here as a caution, the YouTube clip was previously deleted.

Senior Pilot

Richard Godfrey has completely ignored that fact that the speed was reducing all the way down the descent. He has hypothesised a steady descent angle at around 3.5:1 and therefore concluded that one engine had stopped and the other was on ~10,000lb of thrust because, at the initial speed they needed that thrust to counter the drag. But the AOA clearly increases markedly as the aircraft approaches the ground, which means that the speed was reducing significantly.

As for statements such as:
They make me take that whole spiel with a grain of salt.

In a nutshell, he's saying they had an engine failure before rotation, then got all the way up to 300-odd feet (following what looked to me like an initially standard low-angle/flat 787 takeoff, then ran out of puff and crashed with the other engine running at 15-18% Thrust.

Pure speculation aka WAG.

An "expert" who can't get something as basic as a runway slope calculation anything close to correct doesn't inspire much confidence in his other "analysis".

I agree 100% with your last sentence.

Just before posting this reply, I noticed that nachtmusak posted something similar to what I wrote below. Since I spent quite a lot of time and effort fact checking that document and composing this reply, and I think it might clarify things a bit further, I decided to still post this. I'm not a pilot, my main field is software engineering but I also studied power engineering for a while. Watching the aviation world is just a hobby. I've read all posts in both threads since the beginning, but so far I refrained from making a post of my own. If this post is considered redundant, I don't have a problem with it is deleted.

Richard Godfrey first 7 points seem accurate as far as I can tell, but he makes a lot of mistakes at point 8, when he computes the altitude the aircraft reached. The first error is when he said "At liftoff from 180 feet AMSL, barometric altimeter would read: Pressure (ISA) = 1006.68 hPa." While that is correct, that only applies when the QNH is 1013.25. But the QNH was 1001.1, so the altimeter would actually read around 994.6 hPa.

He then said: "Aircraft later reported: Pressure = 990.573 hPa (corresponds to 625 feet in ISA conditions).". That is correct. Then he subtracts the two numbers, 1006.68 hPa and 990.573 hPa and gets a 16.107 hPa difference, which is wrong, since the field level pressure he uses is wrong, as mentioned earlier. The correct number would be 994.6 hPa - 990.573 hPa = 4.027 hPa difference. Using the approximation of 30 ft/hPA, gives us an actual around 120 ft altitude over the field (+/-12.5ft since the aircraft reported altitude has a 25ft granularity).

Instead, he gets a much higher altitude of 480ft over the field and, as a further mistake, he misinterprets it as altitude over sea level, so he subtracts 180ft (the field's altitude). This second error bring the value closer to reality, around 300ft, but still a long way from the correct value which would be around 120ft. I also did a quicker back of the envelope calculation with a different method, and got 80ft +/- 12.5ft, even further from his 300ft.

Then, he makes a third mistake, he assumes that the last altitude reported by the aircraft is the peak altitude it reached, when in fact it is almost certain the aircraft kept climbing for a while after the last ADS-B datapoint (the last datapoint was reported when the aircraft was still above the runway). So it might have indeed reached 200ft or more after all.

Finally, at point 9, he makes an estimation based on the ratio between the wing span and the altitude in the CCTV video, compared to the actual wing span. That's a good idea in theory, but you need the camera to be exactly behind the aircraft and very far away not to be affected by perspective significantly. For example, if you film the aircraft from a 45 degrees angle, the apparent wingspan would be reduced by about 30%.

I didn't fact check points 10 to 19, since most of them relied on incorrect numbers computed earlier.

@Sailvi767, thank you for that video. Nice illustration.

About the previous video regarding Air India Flight 171: when Geoffrey Thomas said that "the aircraft appears to hover" at about time 2:00, I wondered at what kind of aviation expert he is supposed to be.
The aircraft was in forward flight once it left the ground, and until the flight ended (unless it stalled near the bitter end...FDR should clear that up in due course...but my guess is that it didn't stall even then).
It stopped climbing, sure, but it didn't hover.

Concur with the assessment of "clickbait"

A self-anointed one. He has as much credibility as an aviation expert as Elmer Fudd. That\x92s why the post and video were removed and discussion about anything he raises concluded.

This thread is now meandering in the absence of further information.