AS350B3 - hydraulic pump drive

[3top]

Hi all,
...there is a SUP.20 in the FLM of the AS350B3 - "Hydraulic Pump Drive on MGB".
From the description it is obvious it is NOT a hydraulic pump for the dual-hydraulic system, but an Aux-drive for some application/STC.

BUT - it seems I cannot find anything about any STC or application for which this drive is needed!

Can anyone shed some light on this?

Cheers,

3top

[RVDT]

Possibly,

Back in the day - late 80's early 90's - there was a collaboration between Conair/Frontier helicopters for a fire-fighting belly tank install with EC and the Securite Civile. Apparently it was approved in 1986!

This site (http://www.netpompiers.fr/index.php?id=18) (in French) pretty much explains it. There is a pic of an early B1 with the tank. Note it has an F-W*** registration meaning RESTRICTED or EXPERIMENTAL.

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/299x163/ecureuil_as350_dbf19043f18eb09cc3cc5b6d47e3b4a375317b6d.jpg


I worked alongside a few B1's fitted with the system. Hydraulics are a very high performance and reliable system yet are not cheap - 1800 litres/min anyone? It involved a different bevel reduction housing with additional pad - the mod you are looking at.

It has been taken over by electrical systems which do not require the modified main gearbox. The current electrical tanks work but have quite high maintenance and other "issues".

I have seen some incidents with the current models of electric tanks which people have been lucky to survive. For me they are not very well designed, the drop pattern sucks, the snorkel is in the wrong place, the snorkel material can stretch ........................$%#@! Pumps don't last. But hey you get paid by the hour.

At the time there was also a system built for the Super Puma. I worked alongside a military and a civilian equipped Super Puma in Corsica in 1990!

This was the HBE (hélicoptères bombardier d'eau) division of the Securite Civile.

Fond memories of the times - GPS worked for about 2 hours a day, www was non-existent although in France you had minitel and we averaged about 100 hours per month.

That season (1990) we had about 12 of the following in the south of France and 3 in Spain. Happy days!

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/875x598/1005975_large_852b87baad41c056b5700f86362d9d2ecd83ce75.jpg

[GrayHorizonsHeli]

I am pretty positive that if you have dual hydraulics, that pump drive on the front of the gearbox is indeed for the hydraulics. You dont have a choice to add any thing else off that drive.
what P/N is your MGB assembly?

[RVDT]

Apparently that pad is now used for the 2nd pump on Dual HYD machines. It pre-dates dual hydraulics though.

[3top]

RVDT - thanks for the interesting details!!

Well - the description of SUP.20 pretty eliminates it from being the pump for the dual-hydraulic system would eliminate the use for the described fire-fighting system:

1 GENERAL
An optional mechanical power output on the MGB enables the installation of a supplementary hydraulic pump for specific use.
This output is driven by the MGB spiral bevel gear wheel with a speed of 6000 rpm for a corresponding NR of 386 rpm.
When the hydraulic pump is running off load (no specific equipment is using this specific hydraulic power), the power taken from the MGB must be less than 3 kW so as not to
affect the helicopter's performance.
2 LIMITATIONS
The limitations specified in the basic flight manual and in the flight manual supplements
remain applicable and are supplemented or modified by the following:
- Maximum power consumed by hydraulic pump on load .............. 32 kW,
- Maximum power consumed by hydraulic pump off load .............. 3 kW,
- The use of hydraulic power is prohibited:
 in hover,
 in climb,
 in flight at IAS < 30 kt (56 km/h) and IAS > 80 kt (148 km/h).
3 EMERGENCY PROCEDURES
The emergency procedures specified in the basic flight manual and in the flight manual
supplements remain applicable and are supplemented or modified by the following:
- In case of engine failure or loss of power, IMMEDIATELY shut-down the specific
hydraulically powered system.


SO - there must have been some other application for that hydraulic pump drive....

3top

[RVDT]

3top,

Reading around in circles - the SUP probably covers the fact that the pad when it is installed in the NORMAL category is to keep everyone happy.

When you use the drive the operating category may change to RESTRICTED or EXPERIMENTAL..

Looking at the restrictions you could probably do aerial spraying with it?

The use of hydraulic power is prohibited: in flight at IAS < 30 kt (56 km/h) and IAS > 80 kt (148 km/h)

Ask your friendly tech rep and confuse him as well?

[GrayHorizonsHeli]

Years ago, we had an operator ask about the cost to modify an MGB to use the auxiliary drive to run a generator for geophysical equipment.
the cost was too prohibitive to them at the time.

[SASless]

I am easily confused these days....comes with my approaching senility I assume.

The use of hydraulic power is prohibited:
 in hover,
 in climb,
 in flight at IAS < 30 kt (56 km/h) and IAS > 80 kt (148 km/h

So as long as the aircraft is in level or descending flight between 30-80 its....you can use the "extra hydraulics".

Now what possible use can one get from that?

[3top]

SASless, ....yep!! THAT's THE question!!

Geo-work would fit, but unless it is a "hydraulic electric drive".... what little I flew, either used the regular 150A generator or had a Gasoline-generator on the ring/rectangle....

Obviously, what RVDT says could work, but then even if the machine becomes restricted, it doesn't change the stated restrictions....
obviously they don't want you to over-torque the trans....but WHAT was the intended application??

....I need to ask my "friendly tech rep", as RVDT said.

3top

[helicopterray]

FMS 20 is for mod OP 07-1487, which is power take off for Abex pump. The Abex pump is only for the second dual hydraulic pump, according to the Index of Modifications book. The mod number is quite old, and predates the introduction of the B3 with dual hydraulics, so I wonder if Airbus had drawn up the plans for this gearbox around the same time they created the twinstar, and just not utilized it.