Thanks Fortyodd., but if they were off they wouldn't indicate they were off?

Thought this regarding Transfer pump caution indication might assist those asking why they get turned off in flight......



NOTE

There is an option to have that facility, however I don't believe it is fitted/activated as standard on any UK Police/AA 135's.
The 902 we used to have could display the fuel flow rate and there was occasion where I had the display up in order to have a more accurate idea of how much longer we could stay on task before reaching bingo.

However, this all now boils down to the mantra I remember being drummed into us from the start of the IF phase - 'Always Trust Your Instruments'! :eek:

Art,

"but if they were off they wouldn't indicate they were off?"

Yes they would - but there is a 2 minute delay between turning them off and the captions appearing.

AoF;

I have read through the 112 pages of this thread (although I have a 113 page label displayed), I have searched using the PPRuNe facility, I have read through the technical links, googled, blinged, yahoo'd and even Asked Jeeves, all to no avail;
.
.
... When the main tank is below 100kgs, should one fly in balance according to the 'Ball', the PFD triangle, the supply tank levels, or does balance still remain a highly overrated practise?
:confused:

Sid,
Balance? You mean nose in front, tail fin behind, rotors on top and skids below??

Is 2 out of those 4 good enough?

Sid, what about the red string!

Fortyodd, thanks for humouring me.......it was just nagging at me this morning, but so was the 18 year old Glenfiddich from last night.....just thought, that could be taken in different ways!

I assume the `Fuel pressure`warning is taken from the supply tank to engine line,and also assume that irrespective of other captions/cautions /indications,the `prime` switches are put on immediately.(as they were found to be ).
Are there any other actions to be taken as well...?

Art

I'm occasionally asked 'what planet I'm on'? I have to say it's frequently planet Macallan! A rarified atmosphere with very low gravity. Wonderful to be there, but my word re-entry often smarts a bit!

(135 P2+ Flight Manual)
"WARNING LIGHT INDICATIONS
LOW
FUEL 1
LOW
FUEL 2 and / or
(SYSTEM I) (SYSTEM II)
Conditions/Indications
– Respective supply tank fuel quantity below threshold value
– Warning GONG will be activated
Procedure
1. Fuel quantity indication – Check
If positive fuel indication in the main tank:
2. Both fuel pump XFER sw (F + A) – Check ON
3. Both fuel pump XFER circuit breaker (F + A) – Check in
If FUEL LOW warning light remains on:
4. Air Condition (if installed) – Switch OFF
5. Bleed Air – Switch OFF (If OAT > 5_C)
EFFECTIVITY For helicopters with 680 liters fuel tank (673 liters if selfsealing supplytanks are
installed)
6. LAND WITHIN 8 MINUTES
EFFECTIVITY For helicopters with 710 liters fuel tank (701 liters if selfsealing supplytanks are
installed)
6. LAND WITHIN 10 MINUTES"

For the Eurocopter EC145 UH-72 Lakota: “Indication System Monitoring. If one or more fuel sensors should fail, the respective bar graph will reset to 0. Depending which sensor is affected, the fuel display will indicate 0000 (Supply tanks) or a fuel quantity reading for the main tank (MAIN) is without attitude compensation. In the event of the failure of the left or right fuel sensor in the split supply tank or both main tank sensors, the CAD MISC field will display the caption F QTY FAIL.”

I admit, I didn't read all post of that mega thread, but I read that prelim. AAIB report and have learnt an amazing amount about EC135's fuel system.
I waded thru many ponderings and assumptions about the pilot's action or lack thereof, his choice of landing site etc..

But I'm having trouble aligning some simple "facts":

1. The fact that the MRB and TR seem to show now sign of hitting ground while turning (assuming they'd look different even when turning only at min. power off rpm)
2. The witness' reports of the pub indicate a certain delay between the noise "where the band made the roof collapse (cheers and laugther), band picks up playing again..." and the actual roof/floor collapse (it is a vault, hence people and band were in the cellar, right?)

Considering 1
- either the pilot actually autorotated the ship successfully to the ground (roof actually) and the rotors stopped "fully" (rotor brake..) before falling through the roof
- or he literally slammed onto the roof with rotors stopped (rather unlikely, in the light of statements about local building quality in that area vs. a 2t a/c)

Considering 2 (time span 3-10 secs??)
That witness info insinuates some kind of controlled roof landing. But then I do not see how the blades could have stopped. Are 10 secs enough to stop the rotors ?

Somehow the picture in my mind is a correctly landed EC :D with rotors stopped, on a flimsy roof. Put in a nutshell: had the roof not collapsed noone would have been injured, refuel and take of again, kinda...

Thus:
What is the current forum's "consensus" regarding the last 20 secs before the roof collapsed?

Come on Sid, I'm sure that you know the PFD triangle has nothing to do with balance?

Cheers

TeeS

Reely,

Lots of speculation on your questions right at the start of the whole thread.

Sycamore,

"I assume the `Fuel pressure`warning is taken from the supply tank to engine line," Correct - at the engine end
"and also assume that irrespective of other captions/cautions /indications,the `prime` switches are put on immediately.(as they were found to be ). Not exactly - If there is a fuel pressure caption in flight then, the first action after establishing that the engine is still running is to check the associated supply tank contents. If there is fuel available in the tank then it indicates that either the engine driven pump has failed or you have a leak. The purpose of putting the prime pump on is that if the Fuel Pressure caption goes out then it has proven that the engine driven pump has failed. If, however, the Fuel Pressure caption remains on then you have a fuel leak. If there is no fuel in the supply tank then there is no point in putting the prime pump on.

Are there any other actions to be taken as well...?
Commence drill for single engine shut down unless you are already finals to land.

I know, I read that :ooh:. So what's the (your) working assumption?

Couple of questions about NVG (about which I admit I know nothing; never flown in a role which used them)

• Do they add to or detract from pilot's abaility to see/focus on indications/controls indside the cockpit (in partcular the electrical power selector above/behind his head?
• Where do NVGs draw their power from, and would this source be interrupted by the double flame out?
• The interim report says pilot and 2 x police observers were equipped with NVG: has anyone seen evidence as to whether they were actually wearing/using the NVG at the moment of the accident?

Fortyodd2
Are You really sure about that? AFAIK the caption illuminates as soon as the pumps were switched off. In deed there is a timed delay when the pumps are running dry to prevent the caption coming on and off with low fuel in main tank. That was the case in the very early days of the 135, but was changed afterwards.

skadi

Reely340
With the prime pump switches on, the effect of any air sucked with fuel from the supply tanks would have effectively been reduced to zero until the fuel actually ran out. So when the engines failed due to fuel exhaustion, the effect would have been like flicking a switch to turn them off.

The rotor rpm would drop more quickly than in a simulated engine failure where the throttle is rolled off in a more gradual manner.

Once the rotor stalled the air resistance would slow rotor rotation to effectively zero in less than ten seconds.

The aerodynamic design would tend to keep the aircraft upright while falling, all the heavy bits are mounted below the plane of the rotor disk. The stalled rotors would still exhibit aerodynamic resistance.

The free fall time from 1000 feet is less than 10 seconds, however the aerodynamic resistance of the falling helicopter would probably slow the descent rate to around 20 seconds to impact the ground from 1000 feet. Hence the single return from the aircraft on ground radar showing a height of 400 feet after consistently being tracked at 1000 feet, i.e. it was pinged by radar mid fall.

The roof of the Clutha pub was in no way of flimsy construction. It had been originally constructed to take the weight of several floors of warehousing built above, but since removed. The strength of the roof probably prevented many more casualties in this tragic incident.

The primary mechanical causes of the accident are that the fuel transfer switches to the supply tanks were switched off (for reasons unknown). The prime switches were switched on (possibly mistaken fro the fuel transfer switches). When the engines failed due to fuel starvation, they ran down immediately and without warning due to the prime pumps operating to remove any entrapped air in the fuel being supplied to the engines. The rotor speed decayed significantly faster than in simulated or practise autorotations.

Additionally there may have been problems with the information the pilot was seeing on his flight display and when the second engine stopped, the battery may not have been capable of carrying the system load so effectively all the lights went out in the cockpit.

It is possible that the whole incident arose through two switches being miss selected and a display fault preventing suitable warnings being visible to the pilot. The alternative is that the pilot continued to fly the aircraft ignoring several warnings and in contravention of the directions given in the flight manual and operators procedures. That will be for a fatal accident enquiry to determine.

Reely,

Take a look at pictures of the wreck of the helicopter being craned off the roof.
It's smashed up underneath as much as the Norwegian one that hit the wires recently.

It came down very hard onto a tough and heavy roof that took a while to give way/finish collapsing. I'm sure a thorough structural discussion will be in the final report.

The witness statement of a "tumbling" crashing helicopter, if taken at face value, means that the rotors must have slowed substantially during the descent. Otherwise their angular momentum would prevent easy motion in any direction but yaw.

Fortyodd,

Not trying to be argumentative here.....

Indicated....Actual.....how do we know the 400 Kgs was the actual amount of fuel on board?

Did they rely upon the Aircraft fuel gauge system, does the 135 fuel tank have Internal Markings that can be seen through the Filler for comparison?

My point being....if there was a Fuel Quantity system problem....would that have provided for less fuel than thought?

Not that it would matter in the final analysis really as the real questions that need to be answered is whether the Caution and Warnings operated correctly and if the Supply Tanks Fuel decreasing Contents were being displayed.


Perhaps after the AAIB Final Report comes out.....the Police Operators will take a very honest review of their decisions not to stage Fuel at out lying locations so that their Crews can timely access to Fuel during Operations.....particularly Night Operations when the choices for fuel become quite scarce.

I wonder what the cost of a fuel Stash or two would compare like to the cost of a Crew and helicopter.

Had there been someplace this Crew could have gone for Fuel other than the Heliport....might they have done so and not found themselves in this predicament?