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Helicopter down outside Leicester City Football Club

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Helicopter down outside Leicester City Football Club

Old 28th Nov 2018, 11:24
  #821 (permalink)  
 
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Originally Posted by 212man
How do we know that it was?
212Man from AAIB Special Bulletin:

The helicopter then began a climb on a rearward flight path2 while maintaining a northerly heading. Gear retraction started as it passed through a height of approximately 320 ft. The climb then paused. Heading changes consistent with the direction of pedal movements were recorded initially, then the helicopter entered an increasing right yaw contrary to the pilotís left pedal command. The helicopter reached a radio height3 of approximately 430 ft before descending with a high rotation rate.
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Old 28th Nov 2018, 11:39
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SAS.... I have a job. Please feel free to be discouraged by me maintaining my employment. When I have time I will have another look.
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Old 28th Nov 2018, 11:53
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Originally Posted by DOUBLE BOGEY
212Man from AAIB Special Bulletin:

The helicopter then began a climb on a rearward flight path2 while maintaining a northerly heading. Gear retraction started as it passed through a height of approximately 320 ft. The climb then paused. Heading changes consistent with the direction of pedal movements were recorded initially, then the helicopter entered an increasing right yaw contrary to the pilot’s left pedal command. The helicopter reached a radio height3 of approximately 430 ft before descending with a high rotation rate.
Yes, I've read the report (in fact it was me that posted the link here first). But, where in that paragraph does it state what the TDP height was?

Earlier a poster, who would appear to be familiar with the type, posted this:

The TDP is 115ft + the height of the obstacle in your takeoff path so I’d guess a minimum of 250-300ft.

Last edited by 212man; 28th Nov 2018 at 12:05.
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Old 28th Nov 2018, 12:05
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Chop, take-off profiles are designed to give us the best chance when dealing with an engine failure, and they actually work very well if you stick to the profile when you lose an engine. Sadly, it would be impossible to write a similar profile for the catastrophic tail rotor event because control is effectively lost. It is not lost when an engine fails.

DB. Not sure why the gear was retracted, I haven't flown the 169 and know very little about it. In truth I don't believe it would have made any difference. Clearly, if he had suffered an engine failure before TDP he would have had to be quite slick with the gear but from that height I'm sure he felt he had plenty time to put it down again if required. Personally, I raise the gear when it is of no further use to me (rather than 200 feet on climb out). I normally operate from a 10,000 ft taxiway so I have the option to reject for quite a while.
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Old 28th Nov 2018, 12:11
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Originally Posted by 212man
Yes, I've read the report (in fact it was me that posted the link here first). But, where in that paragraph does it state what the TDP height was?
212Man, I am assuming that as forward flight transition was not attempted prior to the Gear being raised that his calculated TDP had not been reached or indeed missed as events transposed.

I think though, that the salient point is should retractable landing gear be raised prior to achieving a sensible amount of forward airspeed and height. Obviously prior to TDP the gear should of course remain available for a reject. In big helicopter world, as you know, we generally do this at Vy+200 feet. More to avoid distraction between VTOSS and Vy and often to conform to a critical performance profile.

However, if we accept that the landing gear is able to absorb some considerable energy in a high ROD touchdown, then maybe the Vy+200 feet (both conditions having to be met), is a good compromise should the RFM not specify for the operating conditions.

I guess what I am really alluding to is would the outcome in this instance have been improved if the gear remained down to absorb the initial energy at impact.
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Old 28th Nov 2018, 12:28
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I guess what I am really alluding to is would the outcome in this instance have been improved if the gear remained down to absorb the initial energy at impact
Yes, I agree with you that even if they had reached TDP, the logic behind early retraction is not clear, although another poster suggested it has a low gear limit airspeed (which I queried and can only assume is related to it being electrically actuated, not hydraulically). I also agree that the outcome of a heavy landing on the undercarriage is likely to have been different to what actually happened. However, when you look at the Kenya Police AW139 accident where they all survived from a similar rate of descent - also with the gear retracted in a hover - and the relatively low level of obvious structural deformation in the early photos taken before the fire really took hold, in this incident - I shudder to think what was going on inside on the ground.
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Old 28th Nov 2018, 12:36
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Originally Posted by Non-PC Plod
Hmm.... Be interesting to know what regulation you think would ensure a safe profile to get out of a football stadium with a tail rotor failure! Somehow ,I dont think you can avoid exposure to a low speed/high torque environment.
You are obviously correct, however the profile used was designed to mitigate a one of two engines failing, but increases the exposure time on the absolute dependance of the one and only tail rotor. I can't help but think a diagonal forward acceleration from the far downwind corner and a zoom climb at the upwind corner would have resulted in less exposure time and less stress to the tail rotor. This obviously puts more reliance on the engines, but they are very reliable these days and there are two of them!
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Old 28th Nov 2018, 12:52
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Originally Posted by chopjock
I can't help but think a diagonal forward acceleration from the far downwind corner and a zoom climb at the upwind corner would have resulted in less exposure time and less stress to the tail rotor. This obviously puts more reliance on the engines, but they are very reliable these days and there are two of them!
Chopjock, the profile you propose would require reject distance available if the helicopter is above the OEI-IGE Hover Mass. You would also need to prove you could clear the stadium OEI after TDP on the remaining engine. Its really difficult to make this work when the distance available are so short. That's why the Rearwards Profile (VTOL Helipad) was conceived. To overcome these issues.
Having said that, the fact that this, and other TR malfunctions have occurred leading to loss of the aircraft and sometimes occupants, at low speeds means you are making an argument. How does the likelihood of a TR event compare to an OEI before TDP?
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Old 28th Nov 2018, 12:56
  #829 (permalink)  

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Chopjock,

As always you think you know better than those who actually do the job. However, most of us tend to operate the aircraft in accordance with the manufacturer's certificated performance procedures, even those of us not operating for public transport (where it is usually mandatory). It is sometimes a condition of the aircraft insurer (and therefore a requirement / condition of maintaining one's employment status with the operator) and it is always a condition of a CAA congested area written permission.
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Old 28th Nov 2018, 13:04
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Originally Posted by 212man
Yes, I agree with you that even if they had reached TDP, the logic behind early retraction is not clear
Hi 212man, it is a long time since I flew retractable undercarriage aircraft but I always thought/assumed that the gear was retracted as soon as possible after TDP in order to minimise drag during the acceleration to Vtoss/Vy, I do wonder whether this was another hang over from fixed wing A/C where the target speeds are higher and so the drag had a bigger influence. Obviously those operating single pilot might feel there would be more important considerations during a busy stage of flight!

Cheers TeeS
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Old 28th Nov 2018, 13:06
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Originally Posted by ShyTorque
Chopjock,

As always you think you know better than those who actually do the job. However, most of us tend to operate the aircraft in accordance with the manufacturer's certificated performance procedures, even those of us not operating for public transport (where it is usually mandatory). It is sometimes a condition of the aircraft insurer (and therefore a requirement / condition of maintaining one's employment status with the operator) and it is always a condition of a CAA congested area written permission.
Just like what I said earlier...
And they were put in that position by the regulations in the name of safety...
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Old 28th Nov 2018, 13:08
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Chopjock, you are the ultimate laxative.

You continue to put forward your ridiculous views in the face of logic and weight of informed opinion against you. It would not surprise me if you were the twin (or alter ego) of the other fool on this board.

Jim
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Old 28th Nov 2018, 13:11
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Now there is a thought......ONLY two Fools in this Forum!
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Old 28th Nov 2018, 13:13
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Originally Posted by SASless
Now there is a thought......ONLY two Fools in this Forum!
Don't forget me!
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Old 28th Nov 2018, 13:24
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Originally Posted by DOUBLE BOGEY
Chopjock, the profile you propose would require reject distance available if the helicopter is above the OEI-IGE Hover Mass. You would also need to prove you could clear the stadium OEI after TDP on the remaining engine. Its really difficult to make this work when the distance available are so short. That's why the Rearwards Profile (VTOL Helipad) was conceived. To overcome these issues.
Except no consideration at all about longer exposure time and total dependance on the tail rotor...
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Old 28th Nov 2018, 13:47
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Originally Posted by TeeS
Hi 212man, it is a long time since I flew retractable undercarriage aircraft but I always thought/assumed that the gear was retracted as soon as possible after TDP in order to minimise drag during the acceleration to Vtoss/Vy, I do wonder whether this was another hang over from fixed wing A/C where the target speeds are higher and so the drag had a bigger influence. Obviously those operating single pilot might feel there would be more important considerations during a busy stage of flight!

Cheers TeeS
TeeS, no the certification and so hence RFM profiles assume that the gear is left down until Vy and 200 ft agl. for a conventional accelerating departure as it is assumed that the pilot/crew are too busy concentrating on achieving the first segment climb at Vtoss to be operating any other controls. For a procedure where the TDP is already above 200 ft I would assume that retraction would take place at Vy.

and less stress to the tail rotor
Chopjock - what stress are you talking about? This is a tail rotor on a Part 29/CS29 certified modern machine, not something on a balsa wood aeroplane with a wind up propeller. Do you seriously think that a gentle climbing imanoeuvre is somehow placing any components in jeopardy?
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Old 28th Nov 2018, 13:53
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Hi Chopjock, so you have backed your helicopter into the corner, accelerated as fast as possible towards the opposite corner (135m away according to Google Earth and that might just allow you to get to 25-30kts before you hit the far stands) and then 'zoom climbed' at a moment when you guess that your angle of climb will just avoid the stadium roof. Thankfully your one engine (one of my two engines) hasn't stopped because the engines are rather reliable, the climb continues until you get to the top of the stadium roof whereupon you continue an acceleration/climb to a suitable height. If at any time an engine stops (except in the first few seconds of acceleration or on reaching a safe height), the tail rotor quits its job, the rotor head lets go or you just overestimate your guess at what climb angle you were going to achieve, you stand a good chance of killing your passengers. How on earth can you argue that you have reduced any exposure times!!
Cheers
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Old 28th Nov 2018, 14:00
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Chopjock, don't think that the exposure to TR failure poor outcomes is restricted to zero speed hovering. TR Malfunction risks are present throughout the envelope and decrease significantly with speeds above Vy, However, in a twin, TR drive failure anywhere in the envelope turns you effectively into a SEH as an autorotation is generally required. Unless you have a Fenestron behind you whereby your options are significantly increased.

To illustrate my rather awkward point. If we all agreed to depart in accordance with your suggestion (Lets call it the "Corner" profile), losing the TR control or drive anytime in the first 70 knots would see you in a smoking heap. Up to 100 kts in the climb out your arse would be eating the seat cushion and the prospects of survival still 50/50. There are no easy alternatives.

That's why others on this thread (and you have managed to stimulate JimL into a frenzy), think you somewhat lacking in the old common sense department. However, try not to get defensive and think carefully about what I have written. This is nothing new. TR Malfunctions and Drive Failures present limited prospects of success wherever they occur.
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Old 28th Nov 2018, 14:15
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TeeS
How on earth can you argue that you have reduced any exposure times!!
How long does it take to VTOSS using CatA profile V a "Corner" profile?
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Old 28th Nov 2018, 14:17
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Originally Posted by 212man
TeeS, no the certification and so hence RFM profiles assume that the gear is left down until Vy and 200 ft agl. for a conventional accelerating departure as it is assumed that the pilot/crew are too busy concentrating on achieving the first segment climb at Vtoss to be operating any other controls. For a procedure where the TDP is already above 200 ft I would assume that retraction would take place at Vy.
Thanks for that 212man, I hadn't come across that as a certification spec - every day is a learning day :-)
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