Helicopter Engine Inlet Filters

[R. Cal]

It seems that many manufactures and users are moving towards using engine inlet barrier filter systems on their helicopters. I'm talking about the "K&N" style filters, not the age-old EAPS style filters. These new filters use a oil soaked gauze material to catch all the nasties.
On the surface they seem to be a good thing. Keep out all the gunk and the engine [I]must[/I last longer, right? Could they actually be "something for nothing" ?

I see on the recent announcement of the Soloy filter for the AS350 D2 that :

"Performance and design characteristics of the new AFS IBF system allow operation in all environments without restrictions, including operation in falling and blowing snow. No performance penalties are imposed with the system and use of baseline aircraft inlet performance charts are authorized. "

Are any of you out there flying with a filter yet? I'm very curious how these things are actually implemented into operations and flight planning. Meaning, could there really be no performance hit (able to use the normal performance charts) while having a dirty and partially blocked filter in front of the engine? How about snow? I would think snow would build up on the filter and cause some power loss. Perhaps there's an indicator to advise that you're in trouble. What are the increases in workload for the maintainers?

I read that the Army has these filters for the Blackhawk, but that they're not approved for Snow. Same goes for the recently certified S-76 filter. Could Sikorsky know something the other filter folks don't?

Rob

[FloaterNorthWest]

I believe the S76 limit on no flight in following snow was after a particular test in specific snow conditions where the inlet barrier filter became blocked by snow. I believe they have a mod but need to test it in the right snow conditions.

At least with the 76 you have a cockpit gauge to indicate the back pressure behind the filter to indicate it becoming blocked.

Have these after market filter manufacturers tested their filters in all conditions? And do they come with a cockpit gauge?

FNW

[rotorboy]

I have flown the IBF fileter on the 500 and the AS350b2.

I was pretty impressed with the filter in the 500, but the 350 was another story.

Anything above 5000' the b2 became a Jet Ranger. It just wouldnt meet performance specs. Getting it to pass a power check was always interesting. You have to modify the cowl, and the opwerotr I worked for at the time, eventually bought a new cowl and removed it. It was so bad we couldnt make contract spec's. The funny thing was the contract required it, and then they didnt want the thing after they saw the performance.

Right after it the filter was clened it seemed to do OK. But anything hot and high there was serious performance issues.

That said I know of another operator who uses the IBF on a B@ and has not had the same issues.

RB

[LowNr]

R. Cal
We recently fitted an AFS filter to our B2.

I took careful note of power readings before the fit and after and have noticed no change. Very happy with the performance so far. Don't do much hot and high work, so can't comment on that.

We've only serviced it once, since and it was very dirty after less than a 100 hours, in fairly innocuous conditions. Obviously it does filter out most of the junk in the air.

Regards, LowNr

[R. Cal]

Floater -

My thinking was that if Sikorsky failed in some kind of snow, did the others test to the same conditions or environment. I can't imagine that the specific inlet design would matter much between helicopters. If snow clogs a 76 filter, why won't it clog a B2?

If your B2 turns into a 206 above 5000ft, I wonder if the performance charts are properly predicting this. Again, there seems to be a lot of variation to actual max performance with these filters. I hope the filter makers are properly documenting the performance implications.

I looked on the FDC website and found the RFM supplements. I see that they say you should "avoid" operation in IGE or ground operations in snow. Does that mean if I do a patient pickup from a snowy field that I might not get out at MGW ?

[MSP Aviation]

i assume they add these restrictions due to the massive amount of snow present during "whiteout" conditions.

[Ian Corrigible]

FDC/Aerofilter (http://www.fdcaerofilter.com/news_detail.php?nid=1) announced last March that their AS350 AStar IBF had been approved "...for unrestricted flight in falling and blowing snow conditions..." following testing undertaken to meet FAA and TC requirements. Installation of the IBF retains the FM restriction limiting flight to 10 mins in <1500m visibility.

I/C

[Hilife]

Last year I spoke with Sikorsky on the installation of FDC filters on their platforms and initially they expected to see a drop in performance after installation. However to their surprise they observed a slight gain in performance as the filter smoothed out the turbulent air in the inlet plenum into a more stable flow as it entered the engine inlet.

Not sure about the snow issue though, although I would have thought that on the C++ the crew will be able to observe any increasing restriction through the filter on the cockpit indicators.

[Graviman]

...Sikorsky on the installation of FDC filters ... expected to see a drop in performance after installation. However ... a slight gain in performance as the filter smoothed out the turbulent air in the inlet plenum into a more stable flow as it entered the engine inlet.

Now that is interesting, Hilife.


Mart

[TwinHueyMan]

We got IBFs for our Hawks when we passed through Kuwait for a sandbox tour. While I saw no difference in torque or TGT with the bypass doors open and closed (and them be some big bypass doors on the 60's) in any realm of flight, some of the "been there, done that" guys said they hurt the A-models and took away precious power we were going to need. Everyone with L-models flew them and loved them, as did the Navy guys and even some of the National Guard guys with A models. We removed them after a few of our birds turned up with ripped gaskets between the IBF box and the inlet, due to flying with the bypass doors open in cruise flight (which some guys were doing, for no reason, except they "thought" they might be power).

Our APUs have IBFs on them, and every 30-40 acft hours we clean them... we're still in absolute awe at how much crud those things catch. The cleaning method is easy as pie... pop em off, spray em with some K&N brand air filter cleaner, and rinse em out in the shower. Oil em up and they're good as new.

The manuals said not to fly with the IBFs in icing conditions, but I don't think 5% of the Blackhawks in the Army have working main and tail de-ice systems. Our MR blades would probably be the size of telephone poles before the inlet filters clogged up.

I think Vertical magazine had an article on them a while back that said the cleaner, less turbulent, more even flow of air actually decreased TOTs on MD500's and the like, giving a gain in power. Plus, the crud stoppage factor. The 58s have had them for a while, and those guys can't get enough of their virtues. I'm sure a lot of it has to with each aircraft getting its own tailored IBF system, and some are better than others.

-Mike