EC135 Engine Air Intake Question

[balaton]

Hi Guys,


Question: what is the path of the EC135 engine combustion air from the airframe intakes in front of the xmisson cowling to the engine inlet?
Simply could not figure out myself. Really annoying! I have studied dozens of pictures, drawings in the RFM and training manual with zero success.
As you can see in picture (see attachments) there is a titanium firewall between the engine and xmission compartment with only a couple of cutouts for the drive shafts and gen cooling air but nothing for intake air.
Con you help me to solve this mystery? Before drawing some quick conclusions on my technical skill, please consider that I do not have a hand-on experience with the 135. Just curious!
(In the picture there is an inlet barrier filter installed but it has no relevance to my question.)


Appreciate your help,


Tamas

[SilsoeSid]

Hi Balaton,

The openings at the front of the transmission gearbox cowlings are not engine air intakes per se. Primarily they are openings to the oil cooler fans, the round part you can see in these pics.

http://i52.photobucket.com/albums/g11/silsoesid/image_zpsdr8q7ber.jpeg
http://i52.photobucket.com/albums/g11/silsoesid/image_zps0dfdukjr.jpeg

Sorry it's a model pic, but shows the engine bay setup quite clearly for this topic,

https://lh4.googleusercontent.com/-FcRoqvKL6mU/VNkUxhdMZ4I/AAAAAAAAA_U/1VDjAoI5J2g/w800-h533-no/IMG_5484.jpg

Hope that helps :ok:

[[email protected]]

http://www.turbomeca-usa.com/images/stories/products/earrius2b2.pdf

The picture on the second page of the link shows the air doesn't enter the front of the engine assembly but I'm sure there are enough 135 gurus on here to let you know exactly how it gets there.

[wrench1]

balaton:

Engine intake air enters through the openings in the transmission cowl and travels over the xsmn and down the T/R driveshaft "tunnel" where it enters each engine compressor through cutouts in the firewalls.

The aircraft Siloe refers to has a factory particle separator mounted in the engine cowl door. The original air path by the T/R D/S is blocked with panels and all air enters the engine compressor through the inlets door inlets.

W1

[balaton]

Many thanks for your quick response guys. That is what I vaguely suspected: the air is not drawn from the front but from the engine compartment itself.
But:
1. why on earth the IBF in my original pics is located in front of of the transmission cowling? Obviously, its function is to filter engine air. (There is another version of the IBF, it is a big screen located on the engine compartment which supports our concept.)
2. As I learned, the grill on the xmission cowl is the oil cooler outlet, the vent behind the cabin window is for electrics. (See the pic. of the black/white heli.) What left is two small NACA scoops on the top and a rather small grill on the engine cowl. ..and this is for a powerfull engine. Strange!
The model picture is interesting. The silver housing around the engine is the intake box (by my limited knowledge). It has to have an opening somwhere on it. I can't see it from this angle, maybe on the bottom?


Cheers,


Tamas

[balaton]

Sorry winch1, cross-posting. Thanks for your reply, but in the attached picture I can only identify some hoses, the drive shaft and (I think) the gen cooling duct (the silver duct) going through the firewall. Where is the air opening?


Tamas

[balaton]

Ok guys, got it. I've got the lead from wrench1. It is the tail rotor tunel!
It can be clearly seen on SilsoeSid model picture between the two engines.
The two air intake boxes/firewalls are connected to it and that's it.
You saved me a visit to the nerby EMS base and looking dumb.


All the best,
Tamas

[skadi]

Many thanks for your quick response guys. That is what I vaguely suspected: the air is not drawn from the front but from the engine compartment itself.
But:
1. why on earth the IBF in my original pics is located in front of of the transmission cowling? Obviously, its function is to filter engine air. (There is another version of the IBF, it is a big screen located on the engine compartment which supports our concept.)
2. As I learned, the grill on the xmission cowl is the oil cooler outlet, the vent behind the cabin window is for electrics. (See the pic. of the black/white heli.) What left is two small NACA scoops on the top and a rather small grill on the engine cowl. ..and this is for a powerfull engine. Strange!
The model picture is interesting. The silver housing around the engine is the intake box (by my limited knowledge). It has to have an opening somwhere on it. I can't see it from this angle, maybe on the bottom?


Cheers,


Tamas

The system on pic 1 is a different type of particle separator ( pall filter ).
The mentioned silver housing is connected to the T/R D/S area, for the IBF equipped machines, there are mechanical operated bypass doors at this position, which could be opened in case of filterclogging. An accessdoor is located on the outer side of the silver housing, this could be opened for preflight check...

skadi

[RVDT]

The 135 air inlet design is a throwback to the 105.

It does have its failings -

The engines breath from the space where the TRDS passes between the engines.

The downside is that any wayward ty-wrap, lost split pin or lock wire that is misplaced on the XMSN deck will go through the engine.

Maintenance techs need to be extremely vigilant that nothing is left on the transmission deck as it is all part of the engine inlet!!!

In reality the engines actually breath around the mast opening. As any dust or dirt recirculates toward the mast it also goes straight through the engines.

The old particle separator had a seal in this area that never really worked that well.

The later models have a barrier filter available as seen in the pic of the T3/P3. The inlet in this area is standard for a T3/P3 with or without IBF.

On the IBF equipped and/or T3/P3 the engine oil cooler exit duct is moved to the upper part of the cowling so that the engine does not re-ingest hot air.

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRYoVvv-QXJOy9wf3X0BC9LmyVoQUa8O28MDmqbR6UEj7lUCCZ5
http://gaoperator.com/wp-content/uploads/2014/10/Airbus-Helicopters-EC135-rotors.jpg

[skadi]

The downside is that any wayward ty-wrap, lost split pin or lock wire that is misplaced on the XMSN deck will go through the engine.

Not quite correct. There is still a screen in front of the engine inlet, to prevent objects being ingested . On the otherhand, the airstream often changes direction, so that heavier objects will bypass the engine. They will leave the duct through the opening at the aft end of the dog house

skadi

[RVDT]

skadi,

I have lost count of the number of FOD incidents with the 135 over the years.

The screen is pretty large on the engines and the "change of direction" doesn't really exist. Everything that can pass the screen will.

On the otherhand, the airstream often changes direction, so that heavier objects will bypass the engine. They will leave the duct through the opening at the aft end of the dog house

No they don't.

I have maintained and flown the 135 now for about 12 years.

[skadi]

skadi,

I have lost count of the number of FOD incidents with the 135 over the years.

The screen is pretty large on the engines and the "change of direction" doesn't really exist. Everything that can pass the screen will.


On the otherhand, the airstream often changes direction, so that heavier objects will bypass the engine. They will leave the duct through the opening at the aft end of the dog house

No they don't.

I have maintained and flown the 135 now for about 12 years.

I just repeated what I was told during my typerating course in Donauwoerth almost 20 years ago. I asked them about that small opening at the lower end of the doghouse...

C80

[SilsoeSid]

Evening all,

I had a friend around a 135T2i earlier today with the cowlings etc off and was able to get hold of these pics that should hopefully make things clearer;

MRGB Cowling removed, showing the oil cooler fan, screen & ducting.

http://i52.photobucket.com/albums/g11/silsoesid/under%20mrgb_zpscxqayqzs.jpg


MRGB etc, to the upper left of this pic you can see the large tunnelled opening that the intake air is taken from.

http://i52.photobucket.com/albums/g11/silsoesid/Under%20gearbox%20cowling_zpswrhlalxy.jpg


Here you can clearly see the tunnelling. The TRDS being the grey coloured shaft running from the rear of the MRGB through the tunnelling.
The top of the shadowed T shape is the position of the engine air intakes.

http://i52.photobucket.com/albums/g11/silsoesid/rear%20of%20mrgb_zpsxkv0dm7q.jpg


The very end of the tunnelling. (I think this is what RVDT refers to as the end of the doghouse)
The angle is a bit deceptive to give a picture of the cavities, however the intake openings are to the top left and right of the shot.

http://i52.photobucket.com/albums/g11/silsoesid/trds%20bay2_zpsl098dtld.jpg


And here is the intake itself (complete with grass)
By looking at the TRDS and protrusions on the decking and comparing with previous picture, you can see where the intake is in relation to the 'doghouse'.

http://i52.photobucket.com/albums/g11/silsoesid/intake_zps3czfhp8b.jpg

:ok:

[balaton]

Excellent pics! (put into my EC135 folder) Many thanks indeed!




Cheers,


Tamas

[retoocs]

Here's a diagram of the airflow path. Air is coming in through the two openings at the front and through the hole at the top of the doghouse for the rotormast.

The Pall particle separator and FDC IBF work similarly by filtering the air going to the inlets at the front and sealing up the rotormast. In addition FDC has the bypass doors at the top. Both systems require due diligence on making sure all the new seals on the cowling are properly installed for the systems to be effective.

Airbus moved the inlets outboard when they designed their own IBF thereby eliminating the competition from installing the particle separator or IBF on the newer aircrafts. The IBF kit is about 400 man hours to install, which is why the P3/T3 are built that way from the factory. The filters are mounted outboard, while the bypass doors mounted inboard (original air path).