Police helicopter crashes onto Glasgow pub
With the transfer pumps running, when you turn them off, how long does it take for the cautions to come on?
MONITORING
The electrical circuits of the transfer pumps are monitored.
In case of a defective pump, a dry running pump, or a switched off pump,
caution indication is displayed at the CPDS MISC field.
- F PUMP AFT
- F PUMP FWD
The pumps are monitored via a shunt. When the power consumption is
higher than 5 Amps (blocked pump), or longer than ~3 min lower than 2 Amps
(dry running pump), the caution will be triggered.
Another word of caution - where you have a situation as evident in this incident.
If there had been enough time to correct the situation by recovering the fuel in the main tank
to the supply tanks by turning on the F PUMP AFT and F PUMP FWD and attempt a restart, please note that in
a normal speed and attitude for autorotation (i.e. < ~80 knots) the SHED BUS would need to be switched to
EMER after a dual engine failure as the F PUMP AFT is on the SHED BB2!!
SS Sid,
Your answers to the CAD failure are listed in the RFM at 3.3.3 Failure of CAD lane.
There is a list of which cautions are subsequently passed to the VEMD screen.
XFER and PRIME pumps are NOT listed.
Transfer Pumps Off From The Start
Having tried this a couple of times, if the Transfer Pumps are never switched on, the Supply Tank contents start reducing at about 250kgs Main Tank contents. So, if that was the case, they wouldn't have been up as long as they were.
Having tried this a couple of times, if the Transfer Pumps are never switched on, the Supply Tank contents start reducing at about 250kgs Main Tank contents. So, if that was the case, they wouldn't have been up as long as they were.
So in this accident at least one of the XFER must have been on in the first part of the flight.
skadi
Purveyor of Egg Liqueur to Lucifer
SS Sid,
Your answers to the CAD failure are listed in the RFM at 3.3.3 Failure of CAD lane.
There is a list of which cautions are subsequently passed to the VEMD screen.
XFER and PRIME pumps are NOT listed.
Your answers to the CAD failure are listed in the RFM at 3.3.3 Failure of CAD lane.
There is a list of which cautions are subsequently passed to the VEMD screen.
XFER and PRIME pumps are NOT listed.
Thanks again for all the technical blurb about the transfer pumps, but my question was, "If someone with a 135 handy can try something out ... With the transfer pumps running, when you turn them off, how long does it take for the cautions to come on?"
I was hoping for a more practical figure, but up to 3 mins seems about right.
Another word of caution - where you have a situation as evident in this incident.
If there had been enough time to correct the situation by recovering the fuel in the main tank
to the supply tanks by turning on the F PUMP AFT and F PUMP FWD and attempt a restart, please note that in
a normal speed and attitude for autorotation (i.e. < ~80 knots) the SHED BUS would need to be switched to
EMER after a dual engine failure as the F PUMP AFT is on the SHED BB2!!
If there had been enough time to correct the situation by recovering the fuel in the main tank
to the supply tanks by turning on the F PUMP AFT and F PUMP FWD and attempt a restart, please note that in
a normal speed and attitude for autorotation (i.e. < ~80 knots) the SHED BUS would need to be switched to
EMER after a dual engine failure as the F PUMP AFT is on the SHED BB2!!
Reading the report, the earlier task in the area was completed at 1,000 ft alt. Assuming that the task completed on the way home in a similar area was at a similar altitude, let me ask the question …."Given an engine failure or double engine failure over a totally benign airfield during the day at less than 1,000ft aal, let alone over a city at night, would you really be contemplating an engine restart?
If the answer is yes, in a 135, why have they stopped, where is the fuel, how is your balance, which supply tank will be best to draw the fuel from, which engine would you start first?
In relation to your 80kts auto airspeed/aft fuel pump/shed emer reference, which airspeed would you actually be going for?
Max range? - 90kts
Min ROD? - 60kts
Best glide? - 65kts?
Imho, I still think it best to go for the plain auto!
Last edited by SilsoeSid; 26th Feb 2014 at 19:11. Reason: Quoted wrong person - corrected :-(
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It seems to me that the fuel system design/ergonomic issues are only part of the problem. There are also significant operational issues in respect of tasking and flight safety. I don't quite see how anyone can justify tasking to the limit of the envelope as standard operating procedure?
Purveyor of Egg Liqueur to Lucifer
I think I've reached my limit with the factual information we have available for now.
As I see it to sum up;
Is the 76 kgs left in the main the big clue?
As I think we have concluded, the transfer pumps must have been on during the flight, 20 kgs seems to be about the most that will syphon (or whatever the effect is) from the main to supply after the pumps have stopped pumping, and with an airspeed below 80kts there are about 76 kgs unusable should the aft fuel pump not be pumping.
It is likely that the non urgent tasks completed on the way back in, and the final part of the flight trace were were done at 80kts or below. Without a better timeline we can only assume that at this stage the gauges were indicating 47/76/43, plenty to have a quick look around the city on the way back to base.
But it's that moment at around 22:00, when the supply tanks were the only source of fuel, that has to be key. Why wasn't it realised that even without the warnings, with 76kgs in the main that the supply tanks were getting pretty low? I know this happens in normal flight to a certain degree, but I've only seen the supply tanks go down as far as about 38, anything below 35 despite the caution, would start to raise a few hairs.
One thing that sticks in mind from the report is "The forward and aft transfer pumps, situated in the main fuel tank, and the prime pumps in the No 1 and No 2 supply tanks were tested and found to operate correctly in accordance with their factory specification."
Would that (bench?) test ascertain that the pumps would also operate correctly in situ?
Here's waiting the next update, with perhaps the GPS trace and twist grip positions mentioned.
All the best
As I see it to sum up;
Is the 76 kgs left in the main the big clue?
As I think we have concluded, the transfer pumps must have been on during the flight, 20 kgs seems to be about the most that will syphon (or whatever the effect is) from the main to supply after the pumps have stopped pumping, and with an airspeed below 80kts there are about 76 kgs unusable should the aft fuel pump not be pumping.
It is likely that the non urgent tasks completed on the way back in, and the final part of the flight trace were were done at 80kts or below. Without a better timeline we can only assume that at this stage the gauges were indicating 47/76/43, plenty to have a quick look around the city on the way back to base.
But it's that moment at around 22:00, when the supply tanks were the only source of fuel, that has to be key. Why wasn't it realised that even without the warnings, with 76kgs in the main that the supply tanks were getting pretty low? I know this happens in normal flight to a certain degree, but I've only seen the supply tanks go down as far as about 38, anything below 35 despite the caution, would start to raise a few hairs.
One thing that sticks in mind from the report is "The forward and aft transfer pumps, situated in the main fuel tank, and the prime pumps in the No 1 and No 2 supply tanks were tested and found to operate correctly in accordance with their factory specification."
Would that (bench?) test ascertain that the pumps would also operate correctly in situ?
Here's waiting the next update, with perhaps the GPS trace and twist grip positions mentioned.
All the best
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It has been my experience that in normal flight conditions for police ops, cruise-hover-orbit-cruise, that the fwd xfer pump will give indications of run dry at around 125kg fuel in the main tank when in the hover, orbit cycle.
Of note is that the 135 on level ground sits at around 7 degrees nose up and of course many things will effect its attitude once off the ground, including CofG and relative wind.
It's also the case that the fuel qty sensors don't often just go wrong overnight, they degrade due to contamination over years (perhaps why the manufacturer specifies 6% inaccuracy as to be expected). In my experience they seem to be less accurate when asked to display abnormal situations (in police use) such as when attempting to fill the main tank to full, or with abnormally low fuel in the supply tanks. A change of sensors by the engineers has always brought things back to normal for a couple of years.
Some on here are still jumping in with 'startling revelations' that have been covered only a few pages ago, and a few pages before that, and....please read what's been said before wasting your efforts.
And to suggest that the less than half dozen 135 police pilots on here don't understand the fuel system is blatant baiting of those who are trying to explain (often in simplistic but factual terms) to an audience with no knowledge but a huge interest. About level with those who drop in every few days, blame the pilot without reservation and clear off again until appearing a few days later without reading anything in between and make the same blunt pronouncement.
Like Sid, I'll be back when something factual emerges to add to the debate.
Of note is that the 135 on level ground sits at around 7 degrees nose up and of course many things will effect its attitude once off the ground, including CofG and relative wind.
It's also the case that the fuel qty sensors don't often just go wrong overnight, they degrade due to contamination over years (perhaps why the manufacturer specifies 6% inaccuracy as to be expected). In my experience they seem to be less accurate when asked to display abnormal situations (in police use) such as when attempting to fill the main tank to full, or with abnormally low fuel in the supply tanks. A change of sensors by the engineers has always brought things back to normal for a couple of years.
Some on here are still jumping in with 'startling revelations' that have been covered only a few pages ago, and a few pages before that, and....please read what's been said before wasting your efforts.
And to suggest that the less than half dozen 135 police pilots on here don't understand the fuel system is blatant baiting of those who are trying to explain (often in simplistic but factual terms) to an audience with no knowledge but a huge interest. About level with those who drop in every few days, blame the pilot without reservation and clear off again until appearing a few days later without reading anything in between and make the same blunt pronouncement.
Like Sid, I'll be back when something factual emerges to add to the debate.
Purveyor of Egg Liqueur to Lucifer
I don't quite see how anyone can justify tasking to the limit of the envelope as standard operating procedure?
Saying that, having been dispatched to a task the other morning well out of our 'old patch', we ended up having to go into an international airport in order to fuel up to get back to base, everywhere else being closed. We landed with 28kgs in the main, supply tanks full & this was still 13 kgs above the 'final reserve fuel'.
Surely, this isn't so much "tasking to the limit of the envelope" as effective utilisation of the asset and correct fuel planning, isn't it?
Besides the report says, "Final Reserve Fuel being the minimum amount of fuel with which pilots should plan to land."
If you happen to go below that FRF unplanned, isn't that what it's actually for?
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If you have an "envelope" then why not operate to its limits? If it is not safe and sensible then change the envelope. Those ex military amongst us will remember the story...... Boss says turn up on parade at 1400. Adj just to be sure, turn up at 1350. Fly cdr, just tobesure 1340, sgt just to be sure 1330..... Ad nauseum.
If a SAFE limit is 2hrs, then it is SAFE to fly to 1:59 EVERY time
If a SAFE limit is 2hrs, then it is SAFE to fly to 1:59 EVERY time
Besides the report says, "Final Reserve Fuel being the minimum amount of fuel with which pilots should plan to land."
If you happen to go below that FRF unplanned, isn't that what it's actually for?
If you happen to go below that FRF unplanned, isn't that what it's actually for?
FRF or MLA Fuel is "Must Land Now" Fuel Level.
Your 20 Minute Reserve Fuel or 30 Minute (or whatever amounts you use for Day/Night) Reserve Fuel Level is that which you can use for unplanned delays.
The Minimum In-Flight Level is there so Dumb Asses do not run the aircraft completely out of Fuel. That is the result of far too many Pilots trying to get back to the Fuel Pump despite knowing they are really cutting it close.
With respect to final reserve fuel; the JAR rule (which is pragmatic) is that if it is reached it requires an emergency call and a precautionary landing should be undertaken.
The latest ICAO Standard (not yet in place) will be that, at any time that it is anticipated that final reserve fuel will be breached before landing (i.e. when in-flight planning indicates that condition) a 'mayday' call must immediately be made.
Whilst agreeing with the sentiment of Jayteeto's post, he has spoilt it with this statement:
Jim
The latest ICAO Standard (not yet in place) will be that, at any time that it is anticipated that final reserve fuel will be breached before landing (i.e. when in-flight planning indicates that condition) a 'mayday' call must immediately be made.
Whilst agreeing with the sentiment of Jayteeto's post, he has spoilt it with this statement:
If a SAFE limit is 2hrs, then it is SAFE to fly to 1:59 EVERY time
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It it should only be used occasionally, call it a cautionary limit. Safe is safe, there should be no interpretation required by the pilot, otherwise it isn't safe
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Sasless, your understanding of the difference between MLA and FRF and absolute limit to land may differ from others in the industry. If you find you will go into FRF, you declare an emergency and get a priority landing, you don't just land immediately.
Final Reserve Fuel being the minimum amount of fuel with which pilots should plan to land.
Regardless of the endurance you actually achieve during the flight itself (it might be more due tailwind or lots of 60Kt orbits, or vv) FRF is that by which you MUST land, and further, when it becomes apparent that you will land with less then a MAYDAY is required. You might well decide to fly another 20 mins on task with base 25 minutes fuelaway and not make a MAYDAY, as long as you land (wherever) at/by FRF.
One aspect of it is a pre-flight planning restriction to prevent chancers from trying to stretch range "because we'll probably find a tailwind/we never burn that much anyway", the other is to make you land when you reach that figure regardless of what you planned.
Jay,
Are we not saying pretty much the same thing.....except I put a hard limit on the fuel limit....where the JAR's, Jim, You, and others state it is an Emergency, requires a Mayday Call, and an EXPEDITIOUS Landing.
I just forego all that formality and legalese and declare it to be a mandatory land absolutely as quick as possible at the nearest suitable landing spot.
When One begins to use the "Reserve" fuel....that is your notice of a pending fuel emergency.....not after you go through your "Reserve" and then on into your Minimum In-Flight Fuel level.
If we can wait until entering the Minimum In-Flight Fuel level to declare an Emergency OR make a precautionary landing then why have the ordinary everyday Reserve Fuel requirement? Upon beginning to use the standard "Reserve Fuel" is when the Radio calls should start and the Pilot making the decision where and when to land....with the dead line being hitting the Minimum In-Flight Fuel Level.
When I managed an Operation I always told the Pilots....if you need a Fuel Bowser sent to you....then no problem or repercussions beyond asking them to explain how it was they could not get to a fuel point. I also reminded them that landing with less than the Minimum In-Flight Fuel Quantity was Grounds for Dismissal. The cost of sending Fuel to a Pilot was far less than replacing the Aircraft and perhaps the Pilot and Passengers if they were to run out of Fuel and wind up destroying the aircraft and killing themselves and their passengers.
Are we not saying pretty much the same thing.....except I put a hard limit on the fuel limit....where the JAR's, Jim, You, and others state it is an Emergency, requires a Mayday Call, and an EXPEDITIOUS Landing.
I just forego all that formality and legalese and declare it to be a mandatory land absolutely as quick as possible at the nearest suitable landing spot.
When One begins to use the "Reserve" fuel....that is your notice of a pending fuel emergency.....not after you go through your "Reserve" and then on into your Minimum In-Flight Fuel level.
If we can wait until entering the Minimum In-Flight Fuel level to declare an Emergency OR make a precautionary landing then why have the ordinary everyday Reserve Fuel requirement? Upon beginning to use the standard "Reserve Fuel" is when the Radio calls should start and the Pilot making the decision where and when to land....with the dead line being hitting the Minimum In-Flight Fuel Level.
When I managed an Operation I always told the Pilots....if you need a Fuel Bowser sent to you....then no problem or repercussions beyond asking them to explain how it was they could not get to a fuel point. I also reminded them that landing with less than the Minimum In-Flight Fuel Quantity was Grounds for Dismissal. The cost of sending Fuel to a Pilot was far less than replacing the Aircraft and perhaps the Pilot and Passengers if they were to run out of Fuel and wind up destroying the aircraft and killing themselves and their passengers.
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Agreed, I would guess a one way debrief from the boss and regulator would be needed if someone chose to use that fuel
If the Operator instills the mindset that it is far better, safer, and fully expected for the aircraft to be landed upon reaching the Minimum In-Flight Fuel Level....with no adverse action being taken if that is carried out....then we have a situation where Safety is foremost.
The Debrief following such a precautionary landing should be a two way discussion about the circumstances and reasons that led to the Precautionary Landing with a view towards ensuring future events might be avoided by the involved Pilot(s) understanding what mistakes they made and ways to prevent that from happening again.
One should not have need for many of these debriefs....as if you do then there is some serious problems in "Judgement" by the Pilot(s) running out of fuel.
Fuel Management is a critical skill that deserves very little leeway in performance.
Either you are on top of the situation and are able to effectively manage your fuel and arrive at a proper fueling point....even if a diversion is required....or you fail in your duties as Pilot in Command.
We all make mistakes....but some are "Mortal Sins" that get no forgiveness...running out of fuel while in flight is unforgivable. That is why we have the concept of "Minimum In-Flight Fuel" or "Land Right Now Fuel" as I call it.
The Debrief following such a precautionary landing should be a two way discussion about the circumstances and reasons that led to the Precautionary Landing with a view towards ensuring future events might be avoided by the involved Pilot(s) understanding what mistakes they made and ways to prevent that from happening again.
One should not have need for many of these debriefs....as if you do then there is some serious problems in "Judgement" by the Pilot(s) running out of fuel.
Fuel Management is a critical skill that deserves very little leeway in performance.
Either you are on top of the situation and are able to effectively manage your fuel and arrive at a proper fueling point....even if a diversion is required....or you fail in your duties as Pilot in Command.
We all make mistakes....but some are "Mortal Sins" that get no forgiveness...running out of fuel while in flight is unforgivable. That is why we have the concept of "Minimum In-Flight Fuel" or "Land Right Now Fuel" as I call it.
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The clue is in the 'planned'.
What is the reserve in Final Reserve Fuel for then?
Sasless calls FRF "land right now fuel", but the possible consequences of landing 'right now' must surely be worse than using the remaining 20+ minutes of flying time to find a suitable and safe unhurried landing site.
In the course of things, calling it 'Land right now fuel' doesn't make sense.
105 kgs - Final Reserve Fuel - Land right now
68 kgs - FUEL Caution - Land as soon as practicable
48 kgs- LOW FUEL Warning - Land within 10 minutes
(105 kgs NPAS night/hostile area FRF)
Sasless calls FRF "land right now fuel", but the possible consequences of landing 'right now' must surely be worse than using the remaining 20+ minutes of flying time to find a suitable and safe unhurried landing site.
In the course of things, calling it 'Land right now fuel' doesn't make sense.
105 kgs - Final Reserve Fuel - Land right now
68 kgs - FUEL Caution - Land as soon as practicable
48 kgs- LOW FUEL Warning - Land within 10 minutes
(105 kgs NPAS night/hostile area FRF)
What is your "Land Right Now" fuel quantity?
At what level do you accept you have to land?
I pick a quantity that assures me of a safe landing....but still leaving some fuel in the Tank.
At some point Sid....you have to accept you are not going to make it to the fuel point and land short.
I don't care what you call it....how you pick the quantity...but you better have one and it has to be a finite number and upon reaching that fuel level....you have to land otherwise you are running the risk of winding up in a situation where you run out of fuel while still in-flight....which would be a very stupid thing to do.
So Sid....what is your magic number....and when everything goes wrong and you find yourself at that magic fuel level.....what would you do?
The answer is exactly as I had said.....you will land where ever you can.....or do you Sid...just carry on?
If I follow your thinking Sid....using your numbers...it is about 28Kgs of fuel. Which is not very much is it in light of the Fuel Quantity issues that can affect the 135. You comfy and warm betting you have that 28Kgs or whatever you choose?
At what level do you accept you have to land?
I pick a quantity that assures me of a safe landing....but still leaving some fuel in the Tank.
At some point Sid....you have to accept you are not going to make it to the fuel point and land short.
I don't care what you call it....how you pick the quantity...but you better have one and it has to be a finite number and upon reaching that fuel level....you have to land otherwise you are running the risk of winding up in a situation where you run out of fuel while still in-flight....which would be a very stupid thing to do.
So Sid....what is your magic number....and when everything goes wrong and you find yourself at that magic fuel level.....what would you do?
The answer is exactly as I had said.....you will land where ever you can.....or do you Sid...just carry on?
If I follow your thinking Sid....using your numbers...it is about 28Kgs of fuel. Which is not very much is it in light of the Fuel Quantity issues that can affect the 135. You comfy and warm betting you have that 28Kgs or whatever you choose?