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EC135

Old 4th Mar 2004, 01:06
  #81 (permalink)  
 
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Presumably the person who started the thread.
Heliport is offline  
Old 4th Mar 2004, 09:04
  #82 (permalink)  
 
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What shock is that then Giovanni? Do tell us all you know...
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Old 4th Mar 2004, 18:28
  #83 (permalink)  
 
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"Outer Tanks and Flapper Valves"????

According to my information there are no "flapper valves" in this fuel system. As for "outer" tanks, if you are referring to the Supply tanks they are immediately behind the Main tank and share the same hull form shape.

There are a total of 3 tanks, 1 Main tank, and 2 Supply tanks.

In a standard (i.e. not self sealing and prior to aircraft serial number 250) configuration the Main tank contains 565 litres or 452 kgs and the Supply tanks hold 115 litres or 92 kgs. The Supply tanks or divided lengthways by a fence and the RH one has a structural channel running through the bottom that reduces it capacity by 5 litres or 4 kg. In fact part of the Main tank capacity (72 kg ) is physically in the upper space of the Supply tanks and connected by "overflow" channels.

If the transfer pumps were not activated or failed, with simultaneous use the RH engine will stop first and the LH will stop 3-4 minutes later.

The fuel from the Main tank is fed by 2 transfer pumps Forward and Aft in the Main tank to the Supply tanks. This fuel is fed through flex lines which pass through the "overflow channels" to exit into the lower part of the Supply tanks. The "overflow channels" are approximately 50 mm in diameter and the transfer hoses maybe 15 mm. The fuel from the Supply tanks when the quantity is above 92 kg runs through the "overflow channels" back into the Main Tank until it is empty. Each transfer pump is capable of 6.6 litres per minute or about 315 kg/hour or more than 150% of cruise fuel flow. When the fuel level in the Main tank is below the level of where these pumps can pick up they should be selected OFF.

This is detected by the caution indication "F PUMP AFT" or "F PUMP FWD" and is completely normal per the FLM.

Failure of the FWD pump can result in an unusable quantity of as much as 59 kg if above 80 KIAS and is 3.6 kg if below which is effectively the same as normal unusable fuel in this cell.

Failure of the AFT pump can result in as much as 71 kg in the hover reducing to 7.5 kg above 80 KIAS increasing the unusable by 4 kgs.

With a little arithmetic the maximum increase in unusable at the failure of BOTH pumps could be as much as 215 kg in the level attitude. This would be the maximum that you couldn't get to by being a little bit cunning. This of course depends on when both pumps become inactive.

If the fuel is no longer being transferred to the Supply tanks by either gravity or pumps there is 92 kgs remaining of which 86.7 is usable. Due to the shape of the tanks Engine 2 will stop after approximately 23 minutes and then engine 1 after 27 minutes. The "LOW FUEL 1" and "LOW FUEL 2" Warning indications come on at the minimum of 24kg per cell. Hence the procedure "Land within 8 minutes."

The above is based on manufacturer's fuel flow data of 65% Q at SL ISA - give or take.

The Supply tanks are fitted with priming pumps which are only used for starting, the engines do not require boost pumps. Incidentally these pumps are identical to the transfer pumps.

The comment about a dual pump failure is interesting, as granted it has consequences but seems highly unlikely.

When operating at different speeds with low fuel quantity betwen hover and cruise the FUEL PUMP lights will come on and off which is normal and also depends on the location of the C of G.

Subsequent to CPDS Software Version V2100B there is the FUEL caption in the MISC indications if the fuel level in the SUPPLY tanks is below a certain value with fuel remaining in the MAIN tank. (read - Check Transfer pumps ON)

Letsby - Sorry about the bits left out.

Last edited by Giovanni Cento Nove; 4th Mar 2004 at 18:56.
Giovanni Cento Nove is offline  
Old 4th Mar 2004, 19:17
  #84 (permalink)  
 
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Well, well. Now tell us something that we don't know. We certainly
knew all of that. What we still don't know, and even you haven't
given the answer, is at what fuel in the main tank is unusable if
both transfer pumps fail at the same time. If by 215 kgs with a bit
of cunning, you mean pulling nose up to slosh some fuel through the
overflow ports, that's not what we were after.

As I said, even the Eurocopter System Description books don't give
the main tank fuel level at the ports. Going by the schematic
diagram of the fuel tank on the CAD, it would seem to be about 300kg,
with resorting to aerobatics to squeeze out the last drops.
MightyGem is offline  
Old 4th Mar 2004, 21:23
  #85 (permalink)  
 
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I think GCN's response is quite clear - 215 kg.

However, the only way you will really know is to carry out a calibration refuel with the airframe in the attitude for your required answer. Meaning that if you want the data for cruise situation, then the airframe must be levelled at that attitude before the calibration starts.
Fill the tank, litre by litre and observe the point at which the fuel flows into the supply tanks through the ports. This will provide you the answer.
Or off course you could do a calibrated defuel at the required attitude and take out the fuel from the suppy tanks until no more fuel can be exracted and see what's left in the tank.
Head Turner is offline  
Old 4th Mar 2004, 23:41
  #86 (permalink)  
 
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Letsby:

Why have you pulled the thread, Cinquo cento conker has now spent hours repeating what I just said???

What the bloody hell's going on.

Smoke me a kipper skipper............
Thomas coupling is offline  
Old 5th Mar 2004, 00:18
  #87 (permalink)  
 
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Farts actually stink only for the benefit of the deaf.....

ATA 28-10-00 General Description Fuel System

Supply tanks = 92 kgs

Main tank = 452 kgs

72 kgs of the Main tank capacity is actually in the upper undivided part of the Supply tanks above the "overflow channels". Granted this data is not in the cyclic attendants blurb.

92 + 72 = 164

522 - 164 = 358

92 = 56% of 164 which is where the fuel would be level with the bottom of the overflow channels.

Therefore 56% of 358 is 200 kgs. This would only be valid in the level position. 215 as quoted was a rough guess for Granny.

That's twice now MG or would you rather take HT's way and get the tools out and see for real?
Giovanni Cento Nove is offline  
Old 5th Mar 2004, 02:21
  #88 (permalink)  
 
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Ec135

Has anybody dumped the autopilot inadvertantly on the EC135? I've heard it is possible to do and can be exciting when IMC!
chopper dave is offline  
Old 5th Mar 2004, 05:05
  #89 (permalink)  
 
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Cinquecento: I'll have some of that - agreed!
QED
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Old 5th Mar 2004, 15:21
  #90 (permalink)  
 
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Granted, as on most aircraft it is possible to do. Part of the issue may be the SAS/AP DCPL switch being on the cyclic ( At the top, furtherest Left) and on other aircraft the SAS disengagement is somewhere else. You probably wouldn't want to do that in IMC. This will dump EVERYTHING - Yaw SAS, P/R SAS and Pitch Damper and of course the AP will go off in sympathy as it needs it's friends. APMD DCPL is the correct one to use which is right down the bottom on the left. This will cancel all upper AUTOPILOT MODES.

The AUTOPILOT on the 135 can be used ALL the time even in the hover and is normal procedure. The control functions provide much improvement over the standard Y P/R and P. If you wish to turn the AP OFF you should use the switch on the APMS.

One EC135 has come to grief in the UK because the AP did exactly what it was told and the operator was not familiar with the system.
Giovanni Cento Nove is offline  
Old 5th Mar 2004, 16:35
  #91 (permalink)  
 
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GCN:

Do you know where the EC135 report is available ? Or even a few more details of when/where it happened ? I don'#t recall anything in the AAIB bulletins, or the occurrence reports about that.
The Nr Fairy is offline  
Old 5th Mar 2004, 16:43
  #92 (permalink)  
 
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EC135T1 G-SPAU

Probably answers most questions on this thread as it tells you how it all works.
Giovanni Cento Nove is offline  
Old 5th Mar 2004, 16:43
  #93 (permalink)  
 
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EC135

I believe the accident is the Strathclyde Police 135 that came down in bad weather in February 2002. Tail # is G-SPAU and is covered by AAIB report EW/C2002/2/4 Bulletin # 8/2003.
chopper dave is offline  
Old 5th Mar 2004, 17:28
  #94 (permalink)  
 
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Not very scientific, but....

Sat in an extended hover, 5deg nose up; switched off both pumps at about 230kg, supply tanks started to show a reduction at 206kg mains. Then tried the zoom climb at about 20deg nose up - it didn't seem to slop any into the supplies.
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Old 5th Mar 2004, 18:15
  #95 (permalink)  
 
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Probably agrees with the statement that the indications can vary by as much as 6% full tanks to 4% near empty. The fuel indication system does compensate for attitude.

Can't understand the zoom climb thing either. Try flying around with a cup of coffee on the floor. Unless it's turbulent in virtually all manoeuvres you won't spill a drop!
Giovanni Cento Nove is offline  
Old 5th Mar 2004, 23:39
  #96 (permalink)  
 
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The AP on our 135 occasionally dumps itself, along with all the SAS.
Not a problem in VMC, but would probably increase your workload a
bitin IMC, but nothing that should cause too much trouble
to an experienced IFR pilot.
MightyGem is offline  
Old 6th Mar 2004, 00:10
  #97 (permalink)  
 
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Why don't you fix it? Don't tell me you fly around with it like this! Probably operate with a transfer pump U/S as well do you?

You say an experienced IFR pilot would have too much trouble - what about an inexperienced one?

Talk about links in a chain.

Can see the ad now:

Wanted Police Helicopter Pilot

XXXXXXXXXXXX
XXXXXXXXXXX
Must be experienced in inadvertent and constant autopilot failures.

Those not meeting the above requirement need not apply.
Giovanni Cento Nove is offline  
Old 6th Mar 2004, 07:35
  #98 (permalink)  
 
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Giovanni:
Can't understand the zoom climb thing either. Try flying around with a cup of coffee on the floor. Unless it's turbulent in virtually all manoeuvres you won't spill a drop!
The EC 135 sounds as if it has a similar fuel system to the BO105. In the case of the BO, the supply tanks are in front of the main, and they are of equal size so that if the transfer pumps fail both engines will quit within seconds of each other.

When checking out in the BO, we were told of a tall pilot who left his transfer pumps off and subsequently had a dual engine failure because the glareshield of that particular ship blocked his view of the "FUEL LOW" caption. We were told that you might have approx. 20 minutes to flameout in such a case. (I might add here that I remember thinking the requisite "Oh, that'll never happen to ME!") As a hedge against such a brain fart, I got into the habit of always without fail leaving the transfer pump switches on and NEVER shutting them off.

One day, I was shut down, showing another pilot the avionics suite in my ship. To save battery power I had turned the transfer pumps off. You guessed it, I forgot to turn them on at startup next time. I had been airborne for fifteen or twenty minutes, cruising along, fat dumb and happy when I began idly looking around the cabin for no specific reason. When my eyes spied the transfer pump switches, I about had a heart attack. YIKES! The "FUEL LOW" light was not on, and my supply tank quantity gage still showed full. What the...?

Apparently, the ten-degree nose-down attitude of the BO in cruise flight kept enough fuel gravity-feeding from the Main into the Supplies. Or something like that. Whatever, it worked I became forever grateful for that rigid rotor and uncomfortable cruise attitude that I had previously cursed.

Long way of saying, I guess, that a full cup of coffee will spill in a BO105, and that there are ways of getting fuel to transfer other than electronically-assisted.
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Old 6th Mar 2004, 16:02
  #99 (permalink)  
 
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It only happens about once a fortnight, it's not a great problem, it's only a minor inconvenience, it re-engages straight away, we only fly VMC, it's intermittant, it takes time and money to experiment replacing bits, it's the only aircraft we've got, they think it's the gyro, it will be replaced when convenient, we don't go inadvertant.

PS. The transfer pumps work fine. Thanks for your answer on that. It's always nice to find the answer to something your not sure of.
MightyGem is offline  
Old 6th Mar 2004, 20:11
  #100 (permalink)  
 
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Great statement MightyGem "we don't go inadvertent" - how can you plan not to do something you didn't intend to do?????
crab@SAAvn.co.uk is offline  

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