Firefighting Chinook Crash
As well as a possible control Link failure or a swashplate failure, it could also be a Piv or Swiv failure/Jam too. I last worked on D's and it's been some time since then. RIP guys.
It has been a long tome for me too Rigga.......can you recall which servos control the yaw input.....Pivoting or Swiveling Servos?
Also....correct. me if I am wrong....isn't there one place on each servo where Flight Control Systems 1 and 2 can transfer fluid if a seal is leaking?
The indication would be one Sump losing fluid and the other gaining fluid.
John Dixon and I each see the problem beginning with uncontrollable yawing of the aircraft that might have led to other issues.
Also....correct. me if I am wrong....isn't there one place on each servo where Flight Control Systems 1 and 2 can transfer fluid if a seal is leaking?
The indication would be one Sump losing fluid and the other gaining fluid.
John Dixon and I each see the problem beginning with uncontrollable yawing of the aircraft that might have led to other issues.
Many years ago I had a Yaw Channel runaway in a Chinook whilst sitting on the side of a hill unloading troops (luckily on an exercise in deepest Yorkshire!). It was obvious looking out that the front disc was tilting left (into the hill) and we had to use cyclic to prevent it striking the ground; the downside was it increased the right tilt of the rear head to the point the droop stops were beaten to death on the rear head. We initially tried to increase power to lift off, at which point it was obvious yaw control was non existent, and we closed down PDQ. During this the rear blades carried out a sun roof modification to fuselage, and finally one blade ended up embedded in the port pillow tank. In retrospect I dread to think what would have happened if we had lifted off. I believe the reason was given as an autopilot malfunction! it also came out that it had happened a few days before whilst in the cruise but was 'easily' controllable, and the engineers found nothing untoward.
I watched that video and had the feeling of deja vu - there is a point just before it goes out of view when it looks like the aircraft has full 'into turn' yaw input thus indicating some form of loss of yaw control in the hover, and no forward motion to give directional control to get out of it.
My thoughts go out to the crew and their families.
I watched that video and had the feeling of deja vu - there is a point just before it goes out of view when it looks like the aircraft has full 'into turn' yaw input thus indicating some form of loss of yaw control in the hover, and no forward motion to give directional control to get out of it.
My thoughts go out to the crew and their families.
Rumour, Innuendo and Hearsay:
I AM NOT A CHINOOK PILOT
I recall an RCAF pilot telling me +- 20 years ago about a failure mode that caused the aircraft to suddenly want to swap ends in forward flight. Can’t recall if it was a CH-46 Labrador or a CH-47 Chinook. It was apparently a fascinating event requiring a change of undergarments and the intervention of a surgical team to remove the seat cushion.
Vaguely recall his explanation as to what caused it but not enough to speculate. It was either a total failure of some system or sensor or a partial failure of same suddenly inputting incorrect swashplate movements. One rotor suddenly wanting to go left and the other right while in stable fwd flight.
A new Emergency Procedure with some highlighted “Immediate Action Memory Items” was created I believe.
I think that there was an similar incident some time ago that was discussed here or on another Aviation site years ago.
I AM NOT A CHINOOK PILOT
I recall an RCAF pilot telling me +- 20 years ago about a failure mode that caused the aircraft to suddenly want to swap ends in forward flight. Can’t recall if it was a CH-46 Labrador or a CH-47 Chinook. It was apparently a fascinating event requiring a change of undergarments and the intervention of a surgical team to remove the seat cushion.
Vaguely recall his explanation as to what caused it but not enough to speculate. It was either a total failure of some system or sensor or a partial failure of same suddenly inputting incorrect swashplate movements. One rotor suddenly wanting to go left and the other right while in stable fwd flight.
A new Emergency Procedure with some highlighted “Immediate Action Memory Items” was created I believe.
I think that there was an similar incident some time ago that was discussed here or on another Aviation site years ago.
Last edited by albatross; 16th Aug 2022 at 21:59.
Shackman,
In the aircraft you had the SAS runaway....how would you describe the SAS system on yours to an American equivalent Model of the Chinook?
I am familiar with the US A, B, C-, and C models but not the D or later models and certainly not the many RAF versions.
On the three models I flew....there was a single Red Guarded Switch that turned the SAS ON and OFF. The C- and C model had the same plus a PSAS system for Pitch Attitude Hold.
On the machines I flew a quick flip of the Red Guard and Toggle With....and in theory the SAS links would have reentered or at least stayed where they were.
On some steepish slopes I have had some Droop Stop Pounding but never any damage.
I have had the unique thrill to hear them really clattering while in flight in the A Model when in a weak moment I turned the SAS off on a Student in a steepish turn and the aircraft got away from him and tried to swap ends at a hundred knots IAS....again no damage.
I can imagine yours was an experience that you will not forget....and I am very glad it was you and not me that got that thrill!
We were still learning about them when I started out on them....and flew some with single digit build numbers for the A Models.
The kind with the fixed aft gear with double wheels and had to be ground taxied using the Aft Gear and flight controls only.
In the aircraft you had the SAS runaway....how would you describe the SAS system on yours to an American equivalent Model of the Chinook?
I am familiar with the US A, B, C-, and C models but not the D or later models and certainly not the many RAF versions.
On the three models I flew....there was a single Red Guarded Switch that turned the SAS ON and OFF. The C- and C model had the same plus a PSAS system for Pitch Attitude Hold.
On the machines I flew a quick flip of the Red Guard and Toggle With....and in theory the SAS links would have reentered or at least stayed where they were.
On some steepish slopes I have had some Droop Stop Pounding but never any damage.
I have had the unique thrill to hear them really clattering while in flight in the A Model when in a weak moment I turned the SAS off on a Student in a steepish turn and the aircraft got away from him and tried to swap ends at a hundred knots IAS....again no damage.
I can imagine yours was an experience that you will not forget....and I am very glad it was you and not me that got that thrill!
We were still learning about them when I started out on them....and flew some with single digit build numbers for the A Models.
The kind with the fixed aft gear with double wheels and had to be ground taxied using the Aft Gear and flight controls only.
Undemanded yaw and lowering of thrust/collective lever, apparently the pilot was unable to override or control the failure. I would suspect a Yaw and thrust lower control pallet debonding/detachment in the control closet?
Last edited by chinook240; 17th Aug 2022 at 19:33.
Avoid imitations
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,573
Received 422 Likes
on
222 Posts
There have been at least two other still unexplained, major accidents with Chinooks in U.K. that I know of, that were both possibly caused by critical flying control failures and both causing fatalities of experienced ex-colleagues known to both you and I.
Shy,
Are there Accident Reports available for those two crashes you mention?
Are there Accident Reports available for those two crashes you mention?
Avoid imitations
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,573
Received 422 Likes
on
222 Posts
SAS,
The first accident was in the Falkland Islands in 27/2/1987.
It’s been discussed here before but unfortunately the BOI report has been archived by MOD so I can’t find it.
That aircraft was on a post maintenance check flight and nosedived in almost vertically from about 1,000 feet, with the loss of five POB, I believe.
The second was the more well known and much discussed Mull of Kintyre accident.
The first accident made me determined, as the father of a young family, to avoid getting posted to Chinooks if at all possible. I terminated my commission less than a year before the second accident, which made me think I’d definitely made the correct decision.
The first accident was in the Falkland Islands in 27/2/1987.
It’s been discussed here before but unfortunately the BOI report has been archived by MOD so I can’t find it.
That aircraft was on a post maintenance check flight and nosedived in almost vertically from about 1,000 feet, with the loss of five POB, I believe.
The second was the more well known and much discussed Mull of Kintyre accident.
The first accident made me determined, as the father of a young family, to avoid getting posted to Chinooks if at all possible. I terminated my commission less than a year before the second accident, which made me think I’d definitely made the correct decision.
I an familiar with the Mull of Kintyre accident...and the controversy that surrounds it.
How many Chinook crashes has there been in the Falklands?
One crashed on a hillside, one crashed from a hover immediately following a Transmission replacement, and then there was the fatal crash of the one you mentioned.....am I right on this?
I am thinking three crashes in the Falklands unless I am reading some articles wrong.
How many Chinook crashes has there been in the Falklands?
One crashed on a hillside, one crashed from a hover immediately following a Transmission replacement, and then there was the fatal crash of the one you mentioned.....am I right on this?
I am thinking three crashes in the Falklands unless I am reading some articles wrong.
Gnome de PPRuNe
Join Date: Jan 2002
Location: Too close to Croydon for comfort
Age: 60
Posts: 12,618
Received 293 Likes
on
161 Posts
Avoid imitations
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,573
Received 422 Likes
on
222 Posts
I an familiar with the Mull of Kintyre accident...and the controversy that surrounds it.
The Falklands crash that followed some major maintenance as I recall on face value should be a suspected engineering failure of some kind as a probable cause.
Not saying that it was....but post maintenance crashes usually are.
One thing for sure....the RAF Airworthiness policies and procedures sure seem to take a lot of criticism in the Military Aircrew Forum here at pprune.
The Chinook is as safe as any other design and due to its long time in service beginning since the early 1960's.....and it is still going strong doing work no other helicopter can do....something must be right about it.
I have lost friends in the Chinook...the Huey, Cobra, Bell 212, Bell 412, the 76,109, 61, and 206, so in my view flying any helicopter carries some risk with it.
On two occasions I refused to fly a Huey that had been used in Logging and a some Bell 212's that were just plain junk.
The Falklands crash that followed some major maintenance as I recall on face value should be a suspected engineering failure of some kind as a probable cause.
Not saying that it was....but post maintenance crashes usually are.
One thing for sure....the RAF Airworthiness policies and procedures sure seem to take a lot of criticism in the Military Aircrew Forum here at pprune.
The Chinook is as safe as any other design and due to its long time in service beginning since the early 1960's.....and it is still going strong doing work no other helicopter can do....something must be right about it.
I have lost friends in the Chinook...the Huey, Cobra, Bell 212, Bell 412, the 76,109, 61, and 206, so in my view flying any helicopter carries some risk with it.
On two occasions I refused to fly a Huey that had been used in Logging and a some Bell 212's that were just plain junk.
I still stand by my personal decision.
With as many transmissions the Chinook has....chip lights were always a common event but rarely did we find anything but a bit of fuzz.
The two main gearboxes....driving the Rotorheads had Chip Detectors that could be pulled while in flight which was the way we identified which one it was as both were on a single segment light.
The joke done by the FE's was to take a Ball Bearing about three times the size of the Magnetic Plug and come forward to the cockpit asking what the Pilot's thought of the metal lodged on the magnet.
At one time engine gearboxes had a lot of serious chips being created and we were changing them with real frequency.
Some units had those nose boxes as we called them....actually come to bits with internal failures thus causing an "engine failure" situation through lost input to the rotor train.
The two main gearboxes....driving the Rotorheads had Chip Detectors that could be pulled while in flight which was the way we identified which one it was as both were on a single segment light.
The joke done by the FE's was to take a Ball Bearing about three times the size of the Magnetic Plug and come forward to the cockpit asking what the Pilot's thought of the metal lodged on the magnet.
At one time engine gearboxes had a lot of serious chips being created and we were changing them with real frequency.
Some units had those nose boxes as we called them....actually come to bits with internal failures thus causing an "engine failure" situation through lost input to the rotor train.
Tragic. At the very beginning a dark car is seen to (I think) reverse away quickly from the riverbank. It starts moving BEFORE the aircraft appears to be out of control. Is there a reason it moves away - something is already apparent amiss perhaps? Or is it coincidence? It would be interesting to speak to the driver.
Coning is moderate but it's visible. Looks like thrust is still available but massive tilt.
From the front it appears the front Disc ist tilted to the opposite direction:
This might indicate that it was not a swashplate failure, but rather something in the general yaw control assembly.
On the other hand it could potentially also have been an aft swashplate failure countered by the pilots applying opposite cyclic (which then only worked on the front rotor thereby causing yaw).
Last edited by henra; 17th Aug 2022 at 21:26.
Good observations....also I am thinking the Aft head tilt is greater than the forward head.
We might look at some of the RAF Chinook display videos and compare Aft Head movements to this video we have and see if there are any useful comparisons.
That still photo sure seems to show the Aft Blades in an unusual position.
The fact the two heads operate in reverse from one another complicates matters visually as it is hard to determine which had the failure and which was being used to counter it but we can safely assume it is something in the Yaw Control system that is failure due to the yawing seen in the video.
Chinooks just do not do that on their own normally.....as LTE is not an issue in the Chinook as it might be in a Single Rotor Helicopter.
There are aerodynamic issues that do affect the handling of the Chinook that will bite you but none that would create such a yawing moment or rate of rotation.
You youngsters that can still see....look at the video from the very beginning....and tell me if. you think the Bucket has been filled or not.
My impression is that was not filled as there is no bulging to it....just long and skinny looking.....or perhaps only partially filled.
It also looks to have swung out quite a distance as the video begins.
We might look at some of the RAF Chinook display videos and compare Aft Head movements to this video we have and see if there are any useful comparisons.
That still photo sure seems to show the Aft Blades in an unusual position.
The fact the two heads operate in reverse from one another complicates matters visually as it is hard to determine which had the failure and which was being used to counter it but we can safely assume it is something in the Yaw Control system that is failure due to the yawing seen in the video.
Chinooks just do not do that on their own normally.....as LTE is not an issue in the Chinook as it might be in a Single Rotor Helicopter.
There are aerodynamic issues that do affect the handling of the Chinook that will bite you but none that would create such a yawing moment or rate of rotation.
You youngsters that can still see....look at the video from the very beginning....and tell me if. you think the Bucket has been filled or not.
My impression is that was not filled as there is no bulging to it....just long and skinny looking.....or perhaps only partially filled.
It also looks to have swung out quite a distance as the video begins.
Last edited by SASless; 18th Aug 2022 at 00:47.
To my eye on the video the centre of rotation of the aircraft appears to be the hook, not the nose. Although this is difficult to judge it would imply a failure of yaw control as a whole rather than a failure of the control run to the aft head.
Agree the bucket looks empty - there is slack in the libe during the descent which to my mind wouldn't happen with a full bucket.
With rapid rate of rotation....I wonder what the Centrifugal forces the crew would have experienced.
It has been suggested the rate of rotation could have caused disorientation....which certainly could be a factor in what happened.
It has been suggested the rate of rotation could have caused disorientation....which certainly could be a factor in what happened.