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4th Aug 2018 Junkers JU52 crashed in Switzerland

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4th Aug 2018 Junkers JU52 crashed in Switzerland

Old 28th Jan 2021, 22:34
  #321 (permalink)  
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That video is a useful teaching tool, well done. The pilots made a routing choice I would not have made. Normalization of deviance, perhaps?
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Old 29th Jan 2021, 06:38
  #322 (permalink)  
 
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Of course it is correct: Former swiss air force and Swiss Air pilots killed 20 people by high risk mountain flying.

See, the Ju-Air guys and galls were all hobbyists with regard to their JU52 activities but they were also professional aviatiors, FAs and aircraft maintenance personel (later ones sometimes retired). I was impressed by the level of care those old planes got. Having had family on these planes several times (and once being on them myself), from my impression they were continuously and meticulously maintained, which is a different type of care then commercial airliners need and get in 21st century. I did not worry about the cargo door hinges though. And everybody admitted that the planes were flown slower then when on military duty, and that there was creativity needed when finding someone who would be capable of remanufacturing or reproducing spares for these BMW engines which unfortuneately are far less common than some still in service radial P&Ws.
I would call the operation a professionalized aeroclub with members mainly from SA and the military.

My first reaction on the report:
Impressed - mainly because of the photogrammetric analysis
Second impression:
Raised an Eyebrow - due to the stipulation of performance problems
Third impression:
Sad - because the obvious agenda of the "investigators"

At first the report remided me of the bonmot of the guy with a hammer.
Obviously they have great materials and computer scientists there:
The photogrammetric evaluation is impressive and of course very relevant to the accident.
All that metallurgical condisderations would make a nice bachelors thesis in material sciences - but have zero relevance for the accident.
The amount of effort that went into fusioning, correcting for pressure heights and analyzing every single radar track of every Ju-Air flight for four months before the accident is amazing and I'm not sure this can be substantiated by the aim to analyze August 4th 2018's accident. I don't think something like this has ever been done before.
Instead it gives a hint that the "investigators" might have something else on the agenda.

Something they did not have: Test pilots - or did they not want to?
In the main report SUST claim boldly that HB-HOT did not deliver performance as demostrated back in 1939 in Nazi-Germany.
"The maintenance documents and in particular the records of the test runs and
static tests for the engines fitted in the Junkers Ju 52/3m g4e aircraft, registered
as HB-HOT, prove that at the time of the accident it was no longer possible to
achieve the flight performance that was originally demonstrated".
Now if you look that up in appendix A1.6 the evidence is difference from flight tests from 1939 by Junkers with a recent static test run, and they give five reasons for possible deviations:
• Condition of the engines;
• Adjustment of the control linkage between the main throttle lever and the carburettor;
• Properties of a brake propeller versus an aircraft propeller;
• Different atmospheric conditions;
• Different engine speed measuring devices.
When comparing in flight RPMs with the 1939 figures, they ackowledge that the aircraft is operated with modified (finer) propeller pitch and cannot demonstrate one single data point with comparable environmental conditions.
However without further ado they stipulate that it is proved that "it was no longer possible to achieve the flight performance demonstrated" and that in combination with their metallurgical orgy the aircraft was not airworthy.
So why did they not follow up with one of the three sister aircraft? It would have been easily possible to gain some in flight performance data of these old ladies. Time for the analysis of hundreds of radar tracks but no test flight?

To me this is less an accident report but more of a "we cannot further allow this hobbyists to run a scenic flights airline" and "we cannot allow historic aircraft to be maintained by seasoned equally old mechanics doing the best they can, it has to be done A320 style" report.

Did Ju-Air successfully make the step to AO in EASA-land? Probably not. Should they have to? Maybe with regard to some event society passengers.

However there should be another option for people who are aware and want to take the risk nevertheless: to fly on aircraft that are older then they are themselves.

Now the planes are being rebuild structually and outfitted with P&W Wasps. They will be able to continue to fly scenic flights - but they are no longer "Tante-JUs".
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Old 29th Jan 2021, 08:19
  #323 (permalink)  
 
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Anyone understands why power was REDUCED before flying low into the basin?
Was it an attempt to synch the engines? Or was it just because they wanted to avoid accelerating during their slight descent to "look through" the "eye" on the ridge? Or was it to reduce turbulence?

I am confused as this power reduction is so much in contrary to usual logic, that if you don't have height (AGL), you better have lots of speed and power.

HB-HOT flew past the Tschingelhörner mountain peaks and began to reduce in altitude, dropping more than 15 m in approximately 6 seconds. During this phase, the power of the engines was rapidly reduced by 30 to 50 rpm, which meant that the engines were increasingly running at a similar speed (5) . During this process, the pitch angle increased and the flight path angle continuously became more negative.

(5) This course of events is typical when synchronising the speeds of the engines"
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Old 29th Jan 2021, 10:55
  #324 (permalink)  
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the power of the engines was rapidly reduced by 30 to 50 rpm,
A power reduction of 30 - 50 RPM, while never the better idea when you need the performance, would not have a "make it or break it" effect on a well planned flight. The variability of the moving air in a bowl like that would have more effect on performance than that small power change.
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Old 29th Jan 2021, 13:02
  #325 (permalink)  
 
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Same with
dropping more than 15 m in approximately 6 seconds
What's 2.5m/s up or down when driving through a thermal. Leave alone a lee rotor.
There is a connection being constructed.
30RPM that's 30/60*9/2=2.25Hz change in first harmonic. I wonder how reliable that is anyhow being reconstructed from a consumer electronics device.

Last edited by BDAttitude; 29th Jan 2021 at 13:17.
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Old 29th Jan 2021, 13:09
  #326 (permalink)  
 
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Two captains

Unfortunately often pilot performance goes out of the window when two mates fly together...The confusion one can also see with PF and PNF incident reports such as the recent irish one.
My first carrier had a ridiculous proceedure of the non flying pilot handling the throttles which again wasn't optimal in several ways.
It would appear that one "captain" had his head in the cockpit trying to synchronize the engines and I wouldn't be surprised if the other wasn't aware of what he was doing and vice versa.
Mountain flying as per the French gliding description of below the crest (vol de pente) is a complicated science which has no givens.
It envolves flying at times under a wing span from the face depending on the steepness of the slope, at an initial speed with energy in hand and ALWAYS WITH AN ESCAPE PATH.
In extremis one can be surprised as I was on a slope bordering the quarry adjacent to the Cape Gliding Club where I found myself and student inverted at 200ft agl.
The thermic activity generally follows the up slope even in the lee, breaking away from trigger points, converging above the crests and with down drafts away from the slope and often in the middle between two crests. (Except when the airflow has gone katabatic).
Low performance motorised flying machines are a danger as downdrafts can easily exceed 2,000 fpm and that is without any wave or rotor influence.
Neil Williams, a former British aerobatic champion who had the wing fold on a Zlin, died flying a Spanish Heinkel 111 in the 1970s doing something similar but with his wife and a couple of engineers on board.
Similarly it is thought that Steve Fossett, the round the world baloonist who tried to set a new world record height gain, did something similar.
Neither of these had fare paying pax on board nor the same level of oversight from the regulators.

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Old 29th Jan 2021, 17:51
  #327 (permalink)  
 
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SUST have published their final report into the accident. English version here - https://www.sust.admin.ch/inhalte/AV...B_HB-HOT_E.pdf
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Old 30th Jan 2021, 18:45
  #328 (permalink)  
 
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WOW, what a devastating report. The reality is that regulators almost always simply don't have the people who have the kind of experience to be able to accurately assess the ability of organizations operating aircraft under a "Historically significant aircraft" designation to attain and maintain airworthy aircraft and operate them safely. It is almost entirely up to the operators to step up and make the commitment to do the right things. Unfortunately like the Collins B 17 crash and this accident some ( most ?) organizations are not up to the task.

Sadly I think the day when people will no longer have the opportunity to experience a flight in an amazing historically significant airplane is rapidly coming. Insurance companies and regulators are going to cover their butts by making it impractical to operate these kind of aircraft. Organizations who operate historically significant aircraft have to take a hard look in the mirror and up their game. One more high profile crash with passenger fatalities and I think it is over for everyone....
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Old 31st Jan 2021, 04:33
  #329 (permalink)  
 
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Now the planes are being rebuild structually and outfitted with P&W Wasps. They will be able to continue to fly scenic flights - but they are no longer "Tante-JUs"
The prototype flew with Pratt & Whitney R-1340 Wasp and powered a number of the civil aircraft. The BMW 132 engine was an improved license built P&W Hornet and powered the military aircraft.
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Old 31st Jan 2021, 07:35
  #330 (permalink)  
 
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Originally Posted by Big Pistons Forever View Post
Organizations who operate historically significant aircraft have to take a hard look in the mirror and up their game.
Well said. I don't understand why they risked flying so low around the ridge, when anyone can do that in a more manouverable modern airplane too. It's the aircraft sights, the sounds,, the smell that these vintage aircraft operators must provide in a very safe manner. Taking an old and somewhat performance limited aircraft onto a dangerous flight path just to show that hole in the ridge, which looks exactly the same from a C-182 or a DA42 or a King Air does not make sense to me at all. That low flying task in the mountans had no relevance to the vintage status of the aircraft.
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Old 31st Jan 2021, 09:22
  #331 (permalink)  
 
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Originally Posted by megan View Post
The prototype flew with Pratt & Whitney R-1340 Wasp and powered a number of the civil aircraft. The BMW 132 engine was an improved license built P&W Hornet and powered the military aircraft.
AFAIK the engine was customer specific. At that time every significant country had it's own manufacturer building radial engines based on some P&W license, some with more some with less modifications. For the german speaking countries that would be a BMW132 engine irrespective of military or civil. The Lufthansa aircraft were also requisitioned by the Luftwaffe and already had BMW132s. So in this little part of the world where most of the JUs were flying they would have a BMW engine. Having had the possibility to see them side by side - the Lufthansa "D-AQUI" and three of the Ju-Air four - I can assure you that difference is noticeable visually (engine cowlings) and audibly. So it's kind of sad to see that BMW engine now gone forever.

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Old 31st Jan 2021, 09:24
  #332 (permalink)  
 
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And I guess you alll start to get this video suggested to you by Youtube. While in most cases, you can see multiple escape routes for an engine failure or strong downdrafts, at 5:12 there is a situation similar to the accident site. But I think the site is different. So the regular route over the Alp may have been flown with more than one such high-risk / no turn-back sections.

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Old 1st Feb 2021, 01:35
  #333 (permalink)  
 
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Figures 22 & 23 attempt to show how moving from a downdraft to an updraft can increase angle of attack. Aerodynamically any sudden change in vertical air movement does change angle of attack. Add a sudden tailwind component and you may well be stalled as I have found out in my glider.

In my case I was downwind of a ridge in a 15 kt wind aloft having just turned final. Second hand I heard that another pilot had a similar encounter quite a long time ago.

The rest of the time, people fly the approach without incident.

The crew may have crossed this ridge with a similar flight path many times in the JU52 and other aircraft, but this time the thermals combined with a wind coming from a certain direction with a certain speed that upset the applecart.
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Old 1st Feb 2021, 21:49
  #334 (permalink)  
 
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Interesting. I too wonder about normalisation of deviance. Flying up the centre of the valley, losing the turnaround option, is something I was taught not to do. I was also taught not to fly up a dead end valley like that with a wind on the nose. Almost guaranteed to have some downdraughts, tricky if power is limited. These every experienced pilots must have known this but perhaps had been lulled by repetition and plenty of successful flights before.

The progressive slow raising of the nose suggests a loss of attitude awareness. For mountain flying a lot of emphasis was on the horizon illusion s, with the need to keep checking the instruments. In the French Alps I was warned about the possible rapid loss of airspeed from downdraft to sudden updraft while flying through gusty turbulence near the mountainsides. Again I wonder if time and experience had dulled the concern.

A sobering report, with useful stark reminders.

'Blind Pew' - excellent post, entirely agree with you.

Ouch.
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