Chinook display withdrawn due to fatigue issues

[Martin the Martian]

Posted on Facebook:

https://www.facebook.com/AirbourneEastbourne/photos/a.421946873428.199584.175773028428/10154134199953429/?type=3&theater

I didn't know our Chinooks were getting that knackered.

[NutLoose]

I didn't think the display at Cosford was all that it was cracked up to be..

Surprised they are having issues as its appears to be a pretty restrained display compared to the ones they used to do when it was introduced.

[Art E. Fischler-Reisen]

Bring back the Puma display!

(But it was also stopped, some twenty years ago...).

[PapaDolmio]

The aircraft or the aircrew?

[PapaDolmio]

I didn't think the display at Cosford was all that it was cracked up to be..
.

Is that pun intentional?

[Out Of Trim]

http://www.pprune.org/members/24640-out-of-trim-albums-out-trim-s-photos-picture451-image.jpeg

:cool::ok:

Not surprised really.. I've seen quite a few of their great displays over the years and I did wonder about the fatigue issue. I've never seen a similar full on display by the US Army! :)

[NutLoose]

Yes papa, glad you appreciated it :)

Is the rear pylon twisted in that picture?

[B Fraser]

As Mr Trim has said.


I wondered if any airframes that had been displayed ever flew in a straight line afterwards. First class flying !

[Evalu8ter]

We've been here before (and not just with my flying....). Pretty sure that a comprehensive survey of the HUMS data proved that no limits were being exceeded during the display a few years back. Perhaps the Mk4 has some additional sensors and Boeing are concerned about the impact on the TLCS maintenance profit margin. Shame really - it's probably done Boeing's sales book no harm over the past decade.

The Puma display? At least it was more dynamic than the Merlin one, without the need for a Banana Splits vehicle to try and liven it up.....though, of course, throwing lumps of earth off your undercarriage having gone ploughing with the nose gear is always a crowd pleaser.

OOT - the US Army don't fly the aircraft anything like as hard as we do....hence why some "interesting" corner cases in the flight envelope on later Control Laws were only found by UK pilots once we started flying them. I took a 4000hr US Army pilot flying once for a routine LL training trip on an exercise. He was staggered how we flew the aircraft in terms of height/speed/AoB - all way in excess of US Army norms. Not saying it's right or wrong, we just fly it differently.

[PapaDolmio]

One of our regular frames on 7 many years ago used to roll horrendously down the back end whilst the front was stable (for a Chinook). I was convinced that one day it would break in half and the two bits fly off (albeit briefly) in different directions. Hence I never sat in the middle!

Think it was 980?

[NutLoose]

I remember going to Fleetlands airshow in the early days with the OCU and after throwing the thing around the sky doing the display, (which really impressed the Fleet Air Arm guys with whom I was standing and were there with their new Junglie) for the finale they landed and drove the Landy and 25 pounder out of the back :p


I remember it well because I was told when you hear the APU head back to the cab as they would be getting ready to depart, well they fired it up early to load the landy and gun back in, I hopped the rope and wandered out to the cab, challenged by the crowd control bod I explained I was with the aircraft but in civvies, letting me carry on the crowd line took this as an ok to go get a closer look and followed me lol.

[tartare]

Gob smacking how maneuverable that big slab of aloominum is.
Especially that nose down 180 degree turn and quick stop to a hover they do.
We only ever see them flying slowly and sedately over Sydney harbour (usually in pairs).
I guess they get up to all that special stuff at night when they're carrying the men with black Nomex suits, lots of guns and mad-staring eyes! :E

[Evalu8ter]

PD,
Can't remember 980 being strange to fly (but hey, I could fly a Mk 3 and not notice anything odd....). 777 certainly had a dutch roll when it came back from being Westland's "Hangar Queen" for a couple of years as the TI ac for a load of UOR upgrades.

[TelsBoy]

One of my lasting memories from the Bournemouth airshow 2 years ago was watching a Chinook display, the picture above is instantly memorable. I was stunned at the manoeverability of the machine, and I did wonder what kind of load that was being placed on the rotors!

Think if I was crew/pax I'd have been at the barf bag.

[treadigraph]

I was convinced that one day it would break in half and the two bits fly off (albeit briefly) in different directions


I heard a story some years ago that the CH-46 had a tendency to break in half in its early days, prompting some macabre humour along the lines of "the CH-46 becomes a formation of two CH-23s"... Any truth in that?

[[email protected]]

I did wonder what kind of load that was being placed on the rotors!I think it will be the airframe that is taking the strain rather than the rotors, which just provide the thrust.

The HUMS will have monitored the engines and gearboxes carefully and probably the total G experienced by the fuselage but with two rotors twisting, shaking and pulling the fuselage in different directions, especially in some of those very punchy manoeuvres - it's not a surprise that cracks appear - display flying might not have been included in the planned usage and operational profiles designed to predict fatigue issues.

Great display though.

[NutLoose]

I heard a story some years ago that the CH-46 had a tendency to break in half in its early days, prompting some macabre humour along the lines of "the CH-46 becomes a formation of two CH-23s"... Any truth in that?

I seem to remember a rotor at Coleman in Germany dephasing, passing through the fuselage and slicing an unfortunate crewman in half.

They grounded the fleet and initiated a fleetwide modification to fit a larger bolt in the combining box where the rotorshafts attached, there was I think three at Odious on a goodwill visit at the time ( one with the gear stuck at full extension on one side ) before we got ours, and a Rep came over to do the work and used a drill to ream the holes out, if memory serves me right he destroyed two before the crews stopped him getting near the third, they sat there for ages on the grass awaiting new gearboxes and shafts.
The problem was eventually found to be bad maintenance practice related as instead of turning the drives until they lined up and then installing the bolt, I think they were using a jacking handle against the shaft flange and against a frame to force it in, hence when they fitted the bolt it was under strain, the one in question failed, the rotors dephased, hit each other and sailed straight through the fuselage. But it was a long time ago and my memory is not what it was.


here you go, the incident in question.

https://aviation-safety.net/wikibase/wiki.php?id=56460

[Rigga]

As far as I know, the infamous "de-phasing handle" was never used/installed on UK aircraft...I'm sure someone will confirm otherwise if untrue. Instead we left things pretty much as they were set from the last servicing. If space was an issue the blades came off and blade folding was quite rare.

When I was on 431MU (83-84) I helped stitch a rear pylon together after some 40 'minor' cracks were found.
Later, in my 9+ years on Chinooks on 18, at PCSF and PCMF and on 78, there were some large cracks found about the Cockpit frames aft and fwd under the floor. At the time 'we' mused that it was possibly those big spring things under the seats (STVA's?) wobbling away like crazy things all the time creating small areas of fatigue...no-one listened to us, btw.
I hope all is sorted soon.

[kintyred]

We've been here before (and not just with my flying....). Pretty sure that a comprehensive survey of the HUMS data proved that no limits were being exceeded during the display a few years back.

Er, no. Several years ago I raised the display flying HUMS exceedances with the operators but was given a stiff ignoring.

[Evalu8ter]

Kintyred,
Pretty sure it was looked at when SH was flying the display - however, if you did report it and it was ignored then that's not good....

[SASless]

I am more familiar with the Aircraft bending in the middle and twisting enough to cause large ripples in the Skin when lifting heavy loads on a single hook.

I have seen the Chinook put through her paces in far more dramatic maneuvers than the RAF display which at least tried for "smoothness and grace" as the display was planned and thought out ahead of time.

Our displays were unplanned and spontaneous when it became necessary to avoid riling the locals anymore than they seemed to be due to our presence.

For instance, I am quite sure the RAF Display never pulled up on the Lever until it drooped the Rotor system past he pointl the AC Generators dropped off line.:uhoh:

[NutLoose]

Yes Rigga, Self Tuning Vibration Absorbers if the memory isn't playing tricks, weighed a ton weight and the front of the aircraft appeared to have been built around them.

[tucumseh]

Nutloose

Agreed. Needed a crane to lift them onto the test bed. Incredibly efficient devices. We would place a glass of water on the top, the actuators would be stroking and the water wouldn't ripple.

[ShyTorque]

Let's face it, if you tie two helicopters together, forcing them to fly in very close formation, there are bound to be problems. ;)

I was always suspicious of a design that sat the pilot on a big heavy block and let the aircraft vibrate around him on springs. :oh:

[chinook240]

I guess the vibration reduction measures didn't work!

https://www.flightglobal.com/news/articles/boeing39s-helicopter-hat-trick-50347/

https://www.flightglobal.com/FlightPDFArchive/1998/1998%20-%200368.PDF

[Rigga]

In the "Helicopter-Hat-Trick" article the guy says helicopter airframes will go forever if you repair/replace the broken parts.
This appears quite true, excepting if you don't find the problems or if cracks grow too quickly for you to find them!