Police helicopter crashes onto Glasgow pub
Just a numbered other
Many years ago I was a QHI teaching my student in the circuit at our satellite airfield in a Wessex 5. Nearing the end of the sortie, with fuel low but not critical,, I thought he would benefit from one final circuit which we flew before rtb.
We landed with our minimum fuel allowance and ground tacked to stand, and just as we stopped, a low fuel pressure warning illuminated and one of the engines flamed out.
The associated fuel tank was bone dry, but the gauge I indicated 90 lbs.
Much older technology, but impossible now?
We landed with our minimum fuel allowance and ground tacked to stand, and just as we stopped, a low fuel pressure warning illuminated and one of the engines flamed out.
The associated fuel tank was bone dry, but the gauge I indicated 90 lbs.
Much older technology, but impossible now?
Ark,
No, still possible - hence the Bond grounding mentioned above.
Earlier in this thread I posted a brief description of the "Fuel warning lights sequence" and pointed out that the RED + Audio was a separate system.
Regardless of what the gauge is reading, if the Red + Audio appears then I would believe it and land fairly smart-ish.
That appears to be the case yesterday and the reason behind the Bond grounding.
No, still possible - hence the Bond grounding mentioned above.
Earlier in this thread I posted a brief description of the "Fuel warning lights sequence" and pointed out that the RED + Audio was a separate system.
Regardless of what the gauge is reading, if the Red + Audio appears then I would believe it and land fairly smart-ish.
That appears to be the case yesterday and the reason behind the Bond grounding.
Last edited by Fortyodd2; 12th Dec 2013 at 08:20.
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Still Flying
40 odd and Aeromys - well there was a dark coloured helicopter scrambled (if thats the right term!) of of Clyde Heliport last night about 6pm, I say scrambled as it headed North East over Glasgow - some fast response police cars also heading that way at the same time causing chaos, I was sitting on the Kingston Bridge in a traffic jam watching it.
I assume Bond need continuity of service, wonder how that works if they rob then from other areas.
Believe it or not, when at Uni we had to study the Strathclyde Helicopter deal in accountancy, as it was complete farce financially due to a fundamental error by the Council. I know that on this one Clyde Helicopters had the main helicopter exclusively for the police plus first dibs on another two, and ultimately it was one of the replacements, I think in Irn Bru or Radio Clyde livery that crashed at Eastwood Toll with fatalities in 1990. So I had assumed Bond would have required similar fleet resilience.
I assume Bond need continuity of service, wonder how that works if they rob then from other areas.
Believe it or not, when at Uni we had to study the Strathclyde Helicopter deal in accountancy, as it was complete farce financially due to a fundamental error by the Council. I know that on this one Clyde Helicopters had the main helicopter exclusively for the police plus first dibs on another two, and ultimately it was one of the replacements, I think in Irn Bru or Radio Clyde livery that crashed at Eastwood Toll with fatalities in 1990. So I had assumed Bond would have required similar fleet resilience.
Just a numbered other
Fortyodd,
Yes, and worrying too.
I thought the schematic of the fuel system showed a very odd layout, barely fulfilling the requirement for separate fuel systems for each engine.
It still begs the question ' Which tank(s) did the 95 litres recovered come from?'
Without flipping back to the diagram, from memory it seems possible to starve the engines with a considerable amount remaining in the main tank.
Yes, and worrying too.
I thought the schematic of the fuel system showed a very odd layout, barely fulfilling the requirement for separate fuel systems for each engine.
It still begs the question ' Which tank(s) did the 95 litres recovered come from?'
Without flipping back to the diagram, from memory it seems possible to starve the engines with a considerable amount remaining in the main tank.
Avoid imitations
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It was noted. But in view of lack of any further information on it, why should further discussion on any other aspect come to an immediate halt?
Fuel system - lhs low in cruise
I have noticed a potential anomaly in the fuel system from various descriptions and diagrams on pprune that I have not seen mentioned.
I would presume that there is something that I am not taking into account and that this has been considered by the manufacturers etc.
A diagram of the fuel system is in post 1026[1] by SilsoeSid and RVDT in post 1065 commented that the aircraft cruises left side low and that fuel spills over the "fence" back to the main tank when the left side is low.
After serial no 250 there is no fence and this aircraft is after no. 250.
According to the diagram in post 1026 there are three 50mm ducts that replace the "fence", two on the LHS supply tank and one on the RHS supply tank. Each tank has a center duct and the LHS tank has an additional duct on the extreme LHS.
Assuming that the ducts are all at the same level AND that the "Split Wall" (diagram in post 1026) does not 'leak' between the tanks and that the diagram is accurate there might be a problem here.
In order to achieve the goal of say 1m 30s between "fuel exhausted" engine flameouts it is imperative that if fuel is lost from the supply tanks due to aircraft attitude then it MUST not be the case that more fuel is lost from the LHS tank than from the RHS tank.
As far as I can see the design illustrated in post 1026 differs from this ideal. In a LHS low situation more fuel will be lost from the LHS tank due to the indicated placement of the ducts. This will reduce the 1m 30s margin. Think of it this way, the banking aircraft will lower the extreme left duct more then the center duct in each tank. Unless there is something I am unaware of or not considering this will lower the fuel level in the LHS supply tank more than the RHS supply tank.
Could this result in a near simultaneous engine failure on supply tank exhaustion?
There is a second issue concerning leaning (over) and fuel gauging. Do the fuel gauges maintain accuracy when the aircraft leans in the cruise as described? I mention this since pilots seem to report that the supply tank gauges show a difference between the supply tanks at all times. Is this necessarily a true difference in the cruise attitude?
I may try later to work out an estimate of how much extra fuel would be lost from the LHS tank but I bet someone beats me to it:-)
[1] http://www.pprune.org/rotorheads/528...ml#post8197673
I would presume that there is something that I am not taking into account and that this has been considered by the manufacturers etc.
A diagram of the fuel system is in post 1026[1] by SilsoeSid and RVDT in post 1065 commented that the aircraft cruises left side low and that fuel spills over the "fence" back to the main tank when the left side is low.
After serial no 250 there is no fence and this aircraft is after no. 250.
According to the diagram in post 1026 there are three 50mm ducts that replace the "fence", two on the LHS supply tank and one on the RHS supply tank. Each tank has a center duct and the LHS tank has an additional duct on the extreme LHS.
Assuming that the ducts are all at the same level AND that the "Split Wall" (diagram in post 1026) does not 'leak' between the tanks and that the diagram is accurate there might be a problem here.
In order to achieve the goal of say 1m 30s between "fuel exhausted" engine flameouts it is imperative that if fuel is lost from the supply tanks due to aircraft attitude then it MUST not be the case that more fuel is lost from the LHS tank than from the RHS tank.
As far as I can see the design illustrated in post 1026 differs from this ideal. In a LHS low situation more fuel will be lost from the LHS tank due to the indicated placement of the ducts. This will reduce the 1m 30s margin. Think of it this way, the banking aircraft will lower the extreme left duct more then the center duct in each tank. Unless there is something I am unaware of or not considering this will lower the fuel level in the LHS supply tank more than the RHS supply tank.
Could this result in a near simultaneous engine failure on supply tank exhaustion?
There is a second issue concerning leaning (over) and fuel gauging. Do the fuel gauges maintain accuracy when the aircraft leans in the cruise as described? I mention this since pilots seem to report that the supply tank gauges show a difference between the supply tanks at all times. Is this necessarily a true difference in the cruise attitude?
I may try later to work out an estimate of how much extra fuel would be lost from the LHS tank but I bet someone beats me to it:-)
[1] http://www.pprune.org/rotorheads/528...ml#post8197673
Purveyor of Egg Liqueur to Lucifer
Just to point out that in ttb's post link above, he called me a knob for pointing out that the #2 supply tank was smaller than #1 
How many professional pilots would invest their own money by going to local flight school and practice touch down autos with an instructor?
I have been have been instructing airplanes and helicopters on the side while working as a professional pilot flying medium and heavy twin helicopters.
I have been have been instructing airplanes and helicopters on the side while working as a professional pilot flying medium and heavy twin helicopters.
Ark Royal,
Yes, it is possible to empty both the supply fuel tanks with 95 litres remaining in the main - but you'd have to:
1. Have switched off both transfer pumps or had them fail - either produces a caption.
2. Ignored the Amber FUEL warning - this isn't strictly a sensor, just a specific total of fuel remaining in the supply tanks being reached.
3. Ignored both RED FUEL LOW warnings with Audio as each supply tank got down to it's trigger level, Approx 26 Port and 22 Stbd and ignored the STBD engine shutting down.
Not sure what the "Chatter" is about the fences being removed post ser no 250. Aircraft after that Ser no have a total fuel capacity of 710 Ltrs as opposed to the 680 Ltrs on airframes before that serial. The walls, fences, call them what you will, that separate the 3 compartments of the tank are still there.
Jimjim, The supply tanks hold slightly different quantities of fuel which is why they always read approx 4Kgs different. Specifically designed that way to ensure that one engine quits before the other just in case you missed all the other signs as described above.
Yes, it is possible to empty both the supply fuel tanks with 95 litres remaining in the main - but you'd have to:
1. Have switched off both transfer pumps or had them fail - either produces a caption.
2. Ignored the Amber FUEL warning - this isn't strictly a sensor, just a specific total of fuel remaining in the supply tanks being reached.
3. Ignored both RED FUEL LOW warnings with Audio as each supply tank got down to it's trigger level, Approx 26 Port and 22 Stbd and ignored the STBD engine shutting down.
Not sure what the "Chatter" is about the fences being removed post ser no 250. Aircraft after that Ser no have a total fuel capacity of 710 Ltrs as opposed to the 680 Ltrs on airframes before that serial. The walls, fences, call them what you will, that separate the 3 compartments of the tank are still there.
Jimjim, The supply tanks hold slightly different quantities of fuel which is why they always read approx 4Kgs different. Specifically designed that way to ensure that one engine quits before the other just in case you missed all the other signs as described above.
DAPT
"A little different in real aircraft than simulator plus you would be able to practice making a Mayday call while lowering collective!"
I would agree entirely but would also suggest that when it happens without any warning on a dark night in the middle of nowhere it is very different to having planned and briefed it before hand over a nice big flat airfield and having an instructor whispering guidance in your ear.
"A little different in real aircraft than simulator plus you would be able to practice making a Mayday call while lowering collective!"
I would agree entirely but would also suggest that when it happens without any warning on a dark night in the middle of nowhere it is very different to having planned and briefed it before hand over a nice big flat airfield and having an instructor whispering guidance in your ear.
DAPT I would just say that in an emergency, the main thing to concentrate on is flying the aircraft to a successful landing and no loss of life. To hell with the radio. The person on the end of the radio cannot help you for the immediate future.
As for saying pilots dont understand the systems, im hoping you're joking. How many different types do the guys on here fly? How many of those similar types have slight variations? The 7 aircraft I fly are all the same type but some have switches in different places, albeit only minimal differences.
Our fuel systems are completely different to those being mentioned. We have two tanks and engine driven fuel pumps. We dont need to worry about transferring fuel during flight. Actually its forbidden unless in an emergency.
As for saying pilots dont understand the systems, im hoping you're joking. How many different types do the guys on here fly? How many of those similar types have slight variations? The 7 aircraft I fly are all the same type but some have switches in different places, albeit only minimal differences.
Our fuel systems are completely different to those being mentioned. We have two tanks and engine driven fuel pumps. We dont need to worry about transferring fuel during flight. Actually its forbidden unless in an emergency.
About Pete's post:
Mostly for the benefit of our fixed wing friends, (Hi Chris!
)
I recall from being trained in five different models of helicopter (all military) that the first step if one loses power (single or twin) is "control Nr" which means do just that. Whatever you are doing, keep the Nr in the desired range. (Also true if you lose a single engine on a twin). Collective pitch and cyclic both have influence on that, depending on your mode of flight.
Fly it first.
Whatever the criticisms of Pete's post, if one is in cruise then one is probably at a speed higher than best range, or best RoD, autorotational airspeed, so a part of the transition from cruise when the drive quits would (generally) be controlling Nr (reducing pitch on the blades to stop Nr decay) and some aft cyclic to slow down to your desired speed range. The aft cyclic will load the rotor head a bit, which that tends to make Nr go up, or at least preserve it.
TC's point about choosing an airspeed that gives you better range may be better understood in that light.
HC makes a point that I had forgotten about, and I am glad he raised it.
While various aircraft may have subtly different responses, his point about "don't unload the head if you lose the engines" is a basic helicopter flying matter that our fixed wing brethren may not instinctually have a feel for. (For that matter, unloading the head in a Huey raises the prospect of mast bumping .. but that's going off topic)
The feature in rotor blade / rotary wing design that makes for good autorotative characteristics from air flow up and through the rotor system are on a loaded airfoil, which is "biting" the air, be that airflow be "from top down through the rotor head" in powered flight, or "bottom up" in autorotational descent.
The points of technique, sweet spots, and the varying autorotation cases for a helicopter with high inertia or low inertia heads would (I believe) be covered in the type training so that pilots flying that model know what the machine is likely to do if things go wrong with the power plant.
Chris:
In cruise, as others have noted, one would typically lead with lowering the collective and then aft cyclic, but in a stick and rudder sense, those two inputs would probably go together and be closer to "simultaneous" than not. A previous poster pointed out "control attitude!" which goes hand in hand with the two inputs going together.
"Control Nr, fly the bird."
I'll defer to the current instructors here on what they teach.
There are multiple cases for when and how one enters an auto, as you can see from some of the previous posts, "control Nr" and fly the bird will have some subtle differences depending on the case you encounter.
As I read it, he's referring to pitch on the blades, which is controlled by the collective.
Chris, if you like flying, you'll love flying a helicopter. All of my friends who flew fixed wing and got to try flying a helicopter loved it. It's stick and rudder flying. 
If you get the chance, take it. You won't regret it.
For G0ULI:
You are missing a real treat. Take your rotary wing friends up on their offer the soonest chance you get. You'll enjoy the flying.
(That last encouragement was an unpaid political announcement on behalf of rotary wing pilots everywhere!
)
G0ULI:
no, that's not what's been said.
Well, if you lose the engines and enter VRS, you are in deep sheep dip.
It might be more accurate to summarize some of the discussion as "if the Nr decays below a certain amount, and you stall the rotary wings / main rotor blades, you are truly screwed." That is a risk of happening after you lose the engine drive to the rotor system, not before.
The issue of VRS in powered flight is a different problem of losing lift on the rotating wings while under power, which won't cause you to lose the engine but can cause you to fall / plummet to earth rather than to land as gently as you had intended.
I'll let TC explain VRS to you, as he's passionate on that topic. (See the recent crash near Shetland which lost four lives, long thread on that in this sub forum. A discussion about VRS and IVRS begins here. )
I hadn't grasped the full gravity of stalling the head in unpowered flight before henra brought it up a few pages back, so don't feel bad. I flew helicopters for a number of years and was more concerned about retreating blade stall than Nr low enough to stall the air foils. You learn something new every day.
This may add some weight to the basics at the top of my post for our FW brethren: The prime directive is .. control Nr, fly the aircraft.
Mostly for the benefit of our fixed wing friends, (Hi Chris!
) I recall from being trained in five different models of helicopter (all military) that the first step if one loses power (single or twin) is "control Nr" which means do just that. Whatever you are doing, keep the Nr in the desired range. (Also true if you lose a single engine on a twin). Collective pitch and cyclic both have influence on that, depending on your mode of flight.
Fly it first.
Whatever the criticisms of Pete's post, if one is in cruise then one is probably at a speed higher than best range, or best RoD, autorotational airspeed, so a part of the transition from cruise when the drive quits would (generally) be controlling Nr (reducing pitch on the blades to stop Nr decay) and some aft cyclic to slow down to your desired speed range. The aft cyclic will load the rotor head a bit, which that tends to make Nr go up, or at least preserve it.
TC's point about choosing an airspeed that gives you better range may be better understood in that light.
HC makes a point that I had forgotten about, and I am glad he raised it.
If you floor the collective without moving the cyclic, everything flies up to the roof as the g falls below zero. Zero or negative g means no significant autorotational effect and the Nr plummets whilst IAS increase
The feature in rotor blade / rotary wing design that makes for good autorotative characteristics from air flow up and through the rotor system are on a loaded airfoil, which is "biting" the air, be that airflow be "from top down through the rotor head" in powered flight, or "bottom up" in autorotational descent.
The points of technique, sweet spots, and the varying autorotation cases for a helicopter with high inertia or low inertia heads would (I believe) be covered in the type training so that pilots flying that model know what the machine is likely to do if things go wrong with the power plant.
Chris:
1. Cyclic back and pitch down, simultaneously or in that order.
"Control Nr, fly the bird."
I'll defer to the current instructors here on what they teach.
There are multiple cases for when and how one enters an auto, as you can see from some of the previous posts, "control Nr" and fly the bird will have some subtle differences depending on the case you encounter.
Does he mean "pitch-down" in the sense of the a/c attitude, or is he referring to the collective lever?
(BTW, not planning on trying to fly a heli any time soon!)
If you get the chance, take it. You won't regret it. For G0ULI:
You are missing a real treat. Take your rotary wing friends up on their offer the soonest chance you get. You'll enjoy the flying.
(That last encouragement was an unpaid political announcement on behalf of rotary wing pilots everywhere!
)G0ULI:
It would seem from the answers in this forum and information elsewhere that something such as a vortex ring formation could in theory put a helicopter in such an attitude that the engines would stop from fuel starvation
and in that event, the pilot would have very little time to recover the aircraft.
It might be more accurate to summarize some of the discussion as "if the Nr decays below a certain amount, and you stall the rotary wings / main rotor blades, you are truly screwed." That is a risk of happening after you lose the engine drive to the rotor system, not before.
The issue of VRS in powered flight is a different problem of losing lift on the rotating wings while under power, which won't cause you to lose the engine but can cause you to fall / plummet to earth rather than to land as gently as you had intended.
I'll let TC explain VRS to you, as he's passionate on that topic. (See the recent crash near Shetland which lost four lives, long thread on that in this sub forum. A discussion about VRS and IVRS begins here. )
I never knew that the main rotor rpm had to be constrained to within such tight limits or fully appreciated that a full main rotor stall would be unrecoverable irrespective of altitude.
This may add some weight to the basics at the top of my post for our FW brethren: The prime directive is .. control Nr, fly the aircraft.
Last edited by Lonewolf_50; 12th Dec 2013 at 14:13.
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"control Nr" and fly the bird
I remember the mantra "Thy rotor rpm are thy staff of life - without it thou will surely perish".
Always seemed to make sense to me, and further, worrying about a rrpm overspeed should be the last of your worries, the more rrpm when it comes to that final - one chance only - pull up on the collective the better.
D
I remember the mantra "Thy rotor rpm are thy staff of life - without it thou will surely perish".
Always seemed to make sense to me, and further, worrying about a rrpm overspeed should be the last of your worries, the more rrpm when it comes to that final - one chance only - pull up on the collective the better.
D
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Fenestron again
DAPT - thank you for posting a link to technical specifications. It would seem that the P2-T2 does have hydraulic assist in the fenestron hub. Detail can be seen in walkaround pics like this one:
credit: pierric boudehen on prime portal
I cannot find any drawing of the gears but I might expect to see a rotation ratio of, say, 5:1, with actual tooth ratio of say 51:11 so as to maintain even wear. If there were to be localised tooth damage on both gears then the damaged areas would meet only infrequently, which might account for the periodic graunching noises heard by one earwitness.
credit: pierric boudehen on prime portal
I cannot find any drawing of the gears but I might expect to see a rotation ratio of, say, 5:1, with actual tooth ratio of say 51:11 so as to maintain even wear. If there were to be localised tooth damage on both gears then the damaged areas would meet only infrequently, which might account for the periodic graunching noises heard by one earwitness.
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If I was Bond just taking account of some of the posts in this thread alone I would be feeling pretty risk averse and taking no chances.
If there is doubt there is no doubt.
I don't think any of their actions necessarily reflect any cause of this accident though at this point.
If there is doubt there is no doubt.
I don't think any of their actions necessarily reflect any cause of this accident though at this point.
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Transfer pumps and N/R VALVES
My post 1102 page 56 outlined my concern of the above. Pitch change requires both to work.
At fuel levels below around 70kgs both must be working to maintain transfer to cater for pitch change.
At fuel levels below around 70kgs both must be working to maintain transfer to cater for pitch change.