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JU52 HB-HOT down near Flims

Maoraigh wrote:

Why would this accident be density altitude related?

Temperature has quite a large effect on density altitude.
Density altitude in feet = pressure altitude in feet + (120 x (OAT – ISA temperature))
I have an instrument that calculates it from the OAT and displays it at the flick of a switch.
Simon


Peter wrote:

I measured it up on google maps at roughtly 200m wide at the crash altitude, so it looks like they flew up the canyon

Classic dead end canyon. Many have perished that way (e.g. in Papua New Guinea) by taking the wrong turn. We’ll have to wait and see whether they can figure out a contributing factor such as engine trouble, or whether the scenario is entirely different to what it appears to be at first sight …. :(

Archie wrote:

Classic dead end canyon.

According to eye withnesses they were flying at about 10 to 11’000 ft, so not in the canyon but well above it. 10’k ft is more than enough to cross the pass and as there is a very popular sight there (The Martinsloch, a hole in the rocks which is visible on some crash pics) the Junkers fleet is well known by the regulars to pass over there. They were originally tracking pretty much in the center towards the north, that would mean slightly to the left of the Piz Segnas in the picture. When they turned left towards the pass, they flipped over and went down straight. There are many eye withnesses who saw this from quite close quarters, including the keeper of the lodge on the pass. The statement from those at the pass was that the plane was well above them when the upset started.

About 10 minutes before the accident, a former military pilot (and likely one who flew the JU himself or at least on it) saw the plane crossing over his position “in the valley” and saw the plane initiating a left turn and going abruptly nose down to the left. He then heard a massive howl of engine sound and the plane recovered and continued “normal flight”.

These observations are quite significant I think. The keeper of the lodge was well used to the JU fleet passing overhead and knows how that normally looks like. The military pilot should be quite a good withness as well as he would reckognize the attitude and maneuvers better than a layman.

Given that the temperatures up there were close to ISA+20 the question must be asked whether the plane was operating near its absolute ceiling for the weight they had. The question then arises what happens at that density altitude with stall speed at bank angles. The other question which has been raised is if the airplane was operating on non-leaded fuel, for which they have authorisation. However, automotive fuel is not unknown to produce vapour lock and there the temperatures could have had a very undesirable effect. If they lost one or more engines even temporarily during the turns, this could have a massive consequence.

Last news is that the grounding of the fleet by JU Air was volontary in order to make time to get over this tragedy for them and their 160 volonteers. They are planning to resume flight operations somewhen around August 18th, provided nothing surfaces in the investigation which would preclude that.

LSZH(work) LSZF (GA base), Switzerland

Was this a Ju 52/3m (I.e. the three engines variant)? Wikipedia gives a service ceiling of 11200ft for the one-engined variant Ju 52/1 vs 17100 ft for the Ju52/3m , though this seems to further depend on the exact variant.

Low-hours pilot
EDVM Hildesheim, Germany

MedEwok wrote:

Was this a Ju 52/3m (I.e. the three engines variant)?

Yes. I don’t think there is a single engine one still flying.

However, the original performance figures will not apply. For noise reasons they are restricted to 500 hp per engine, which means 300 hp less all in all. I understood that the service ceiling is around 13000 ft, so with the DA of the day, they were pretty much there.

LSZH(work) LSZF (GA base), Switzerland

But, definition, aircraft can still climb at their service ceiling, albeit slowly; it’s not as if they just fall out of the sky, like this.

EGKB Biggin Hill

I have many times gone as high as the plane would go. The first thing is you get the stall warner; this happens some 5-10kt before the buffet onset. The plane doesn’t just plummet, drop a wing, etc.

OTOH I know nothing about the JU52 which dates to before there was any certification climate and which for all I know might have some weird behaviour near the ceiling.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

I have many times gone as high as the plane would go. The first thing is you get the stall warner; this happens some 5-10kt before the buffet onset.

It may not have a stall warner or even much aerodynamic warning of an oncoming stall. Aircraft of that era weren’t built to quite the same standards that we are used to.

We had an incident (fortunately nonfatal, unfortunately with serious injury) of the “clutching hand” with the result that an underpowered aircraft crashed. I almost eyewitnessed it, I only didn’t because my nose was pitched up for climb at the time. The aircraft in front of me, which was criticially underpowered (we watched them test fly it on earlier occasions and the climb rate was anaemic to put it charitably) got caught in the curl over from the Bride Hills (a terminal moraine north of Andreas with a height probably not exceeding 250 ft). They tried to turn away from the hills, but any aerodynamic warning of a stall was probably masked by turbulence, and the aircraft departed controlled flight and fenceposted – what saved their lives is that they crashed going downhill so the aircraft didn’t come to a sudden stop but skidded down a steep embankment before coming to rest. A pilot on the ground described basically a spin entry.

I’ve not seen any mention of wind strength and wind direction for the Junkers crash, but may it have been a case of ‘the clutching hand’, high weight, and not enough airspeed?

Last Edited by alioth at 07 Aug 08:53
Andreas IOM

Mooney_Driver wrote:

For noise reasons they are restricted to 500 hp per engine, which means 300 hp less all in all.

How are they restricted? Something physical preventing them from going over 500hp per engine, or does the pilot control it by simply not pushing the throttles all the way open? In the latter, if it’s going pear shaped – damn the noise and firewall it.

Andreas IOM

I think mooney drivers’ explanation seems very plausible. It’s never just one problem, but a series of issues together. They must have been fully loaded – they had 17 travellers with baggage on board, not the usual sightseeing crowd without baggage. Combine that with very high temperatures, which means high density altitude, resulting in flying close to the ceiling. Under these conditions, problems with or loss of one engine might have had dramatic consequences.

Safe landings !
EDLN, Germany
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