mjunior

Does fod screens introduce performance reduction in our turbines (for those ones that are originally announced/sold without them)? If yes, is there an average number for such reduction?
Regards.

Dr Honda

My Feedback: (4)

I would say that generally... no... there isn't a reduction. You just need a screen with enough area.

AMTdude

go joggin with different screens duct taped across your mouth and see if it affects how you run, the smaller the mesh the less flow = less performance.

bcovish

My Feedback: (8)

mjunior: One piece of fod thru your turbine for whatever reason and you would have wished that you had a fod screen installed.

AMT dude, you service turbine engines. A piece of fod thru our turbines = more business for you.

mjunior

Bcovish,

I'm totally convinced about the advantages of a FOD screen. What I am trying to figure out is if a turbine with integrated FOD screen (like the Wrens) would be one step ahead of any other turbine that is originally sold without FOD screen (for the same class of thrust of course). Practical example is the wren 100 sold with an integrated FOD screen is announced to provide 22 lbs of thrust. Any other competitor like a Jet Cat P-100 is also sold providing 22 lbs but it doesn't have a FOD screen. Therefore, if I install a screen in a P-100 would it be a bit behind the wren 100 or no?

Regards
PS: also if FOD screen doesn't bring any impact to engine performance why the full scale jets don't have them.....?

rcjetsaok

My Feedback: (7)

I flew AMT's since the beginning.. Many moons.. Never had a FOD screen on one of them.. Never a problem.. Chews it up and spits it out !!! I even tried not feeding it FOD hoping it would loose some weight... Didn't work..


Danno

RCISFUN

My Feedback: (44)

I can comment that from empirical testing of my Jet Central Rabbit and Cheetah on the bench with a FOD screen installed, I achieved advertized thrust numbers using a digital "Fish" scale.

This same digital scale was verified on a set of certified weights.

AMTdude

I am not against fod screens in general... but some have showed up with some pretty fine meshes...these tight mesh screens can limit performance. I dont want anyone to have a problem with their engine, no matter who builds or services it. It could also get suked in if flow is low enough, just like a wire or hose near the bellmouth.

More often an engine that has been near sand or light dirt over time needs bearings, and i dont think you can stop the smaller particulates without choking the engine.

A fod screen could help with big bugs, or large items jarred loose from inside the jet during a flight or in a crash, however the benefits are minimal IMO.

Weather the screen was factory installed or not is irrelevent if it is attached properly, many come in with the screen simply silconed to the front cap, which appears to work just fine.

Dr Honda

My Feedback: (4)

Bugs seem to pass without an issue I sucked a stink bug though my AMT 180, and it never skipped a beat. Actually, it was kind of funny... and the CD who was signing me off said... "you should probably get a FOD screen on that." (lol)

FYI... all my other engines have a FOD screen.

rcpete347

My Feedback: (251)

HI all, of course, FOD screens reduce effeciency, but who can afford to trash your turbine, just something we have to put up with.
PS, I"ve seen some trashed turbines, even with FOD screens on, especially sandy Jet fields.
Rcpete

Boomerang1

Actually, some full size jets do have FOD screens, either on the engines or a fold up flap with
a screen as part of the intake which folds out of the way once the aircraft is safely in the air.

John.

Jack Diaz

My Feedback: (1)

As in everything, there is not a single cure for all potential problems.

A couple of weeks ago, a friend of mine was doing the maiden of an spectacular Tam's F-18 powered by a JC 160SX.
His first landing attempt was hot, so he decided to abort after he was already on the ground (short runway).
The airplane rotated just a foot or two before the end of the runway.
The wild grass around the runway was about one foot high.
The airplane barely touched the grass. BUT (as we discovered later) ingested a few grass leaves that partially blocked the FOD screen.
Plane wasn't able to gain speed. Went into a sort of high alpha. And, ended up in a lake [:@][:@]

Those few leaves would have easily gone thru the engine if it didn't have the screen.

So, I guess that what helps in some situation can hurt you in another one.
We are still in shock for such a freak and costly accident. Plane and electronics are a total loss. Will see about the engine.

BTW the plane owner is Marco Mascia, great friend and Top Gun competitor.

rhklenke

My Feedback: (24)

The basic answer to that question is that modern full-scale turbines have multistage axial-flow turbines that are *much* more sensitive to disruptions in airflow than our simple (and inefficient) single-stage centrifugal-flow compressors.

A FOD screen on a full-scale turbine that was fine enough to catch the kind of small FOD that the engine can suck off the ground (that would be huge FOD for our engines) would totally disrupt the airflow needed by their high efficiency compressors...

Bob

flycatch

My Feedback: (26)

Of course it does. Just compute the total area that airflow is restrcted by the wire mesh.

wojtek

My Feedback: (73)

on some engines it has more of an effect than on others ... A p200 for instance will loose around 2 - 4 lbs thrust with a FOD screen alone, where as a typical 36lbs class turbine wont loose more than 1 lbs from a FOD screen ... it all goes back to air intake areas and how diferent engines are affected by the reduced airflow .. I would personally not fly any jet without a FOD screen . Its only a matter of time before something gets sucked up .


~V~

rctech2k7

My Feedback: (1)

I agree with your first and most responder here including taking effective unrestricted area over the intake... This is also why a FOD screen surface is stretched to get larger lateral area and have negligible effect...

The screen that causes some reduction in the intake causes the engine to run in lower efficiency due to more energy dissipates into heat rather than mechanical output. Depending on ECU parameter the engine is to use more fuel to maintain setpoint rpm. Also the rpm that drives the compressor from drawing more air suppose to cool the temp down.

Exhaust velocity increase in the expense of temperature within ECU condition...

Henke Torphammar

Exactly! If your engine looses power with a FOD screen the screen are not engineerd in the right way. I have only made tests on the small Kolibri turbine and I could not messure any diffrences in thrust or EGT with the FOD screen mounted. I assume that the FOD screen then flows enough.

An install like this did however increase the EGT by 40 celcius over the whole rpm range. The lid infont of the engine sits with magnets so it was easy to try without it. I assume a restrictive FOD screen would do the same.

BaldEagel

JFI I was involved in some work at Gatwick airport, the main contractor had to take out £50 million back too back insurance to cover the airports liability to any aircraft ingesting anything solid over 10mm in dia, hence the constant cleaning of the runways, taxi areas and perry tracks.

Mike

Joe Westrich

My Feedback: (95)

I ran my 200SX on a test stand 4 weeks ago and I ran it with and without the fod screen. The difference was suprisingly minimal. I lost about 3/4 of a pound of thrust. I thought it would be much more,especially since the FOD screen was made for a 160 size turbine. The mesh was coarse but still added a lot of protection. I wish they made a FOD screen special for the 200.

I don't know why full size don't use them....maybe because the higher speeds (well above our 200mph limit) the screens cause major problems.

PaulD

My Feedback: (39)

The recent RCJI turbine test issue had an article on this. The authors conclusion was that there was no measurable difference for the turbine size and fod screen he tested. Most turbines monitor rpm as an upper limit for normal full throttle performance and then use egt as the "safety". A fod screeen that adds restriction is only likely to cause the turbine compressor to work harder and add more fuel to reach the same rpm effectively raising egt temps as Henke experienced on his Funjet. I think your fod screen would have to be really restrictive to push the egt's to the point where the ecu was dialling back fuel flow - but then you have the wrong fod screen for your turbine.

If you're really concerned about performance, put the fod screen on and then put your airframe on a diet. Most of the jets I see are over complicated with stuff that are all nice to haves but don't really contribute to the safety or performance and just add weight.

PaulD

causeitflies

Full scale FOD screens

http://www.youtube.com/watch?v=s5Udo...feature=relmfu

warbirdfanatic

My Feedback: (1)

Those large scale FOD screens are designed for Take off and landing, once the plane would get to a relevant height they would open fully to prevent any crud being picked up which usually began from the landing gear flicking FOD about!

Not sure if many people have done it but FOD guards on the actual canards help if you don't wish to put a guard directly on the engine, in my Mirage 2000 I used 2 sheets of semi course mesh (1mm holes)on the left and right intakes, then internally I had a FOD guard on my JJ1400 as another precaution, I take off on Tarmac and Grass and found the front wheel would flick up a lot of grass, small twigs, grains of dirt etc, it's almost eliminated. If you're adding guards to the intake canards you can actually add several different types of mesh to prevent almost all the specs of potential dust, due to the larger surface area there's no strain on the engine. Another thing you can do is add an actuator to the canard guards to open them up fully once in flight if you felt there would be an air restriction.

BaldEagel

From Wikipedia

"In aeronautics, canard (French for "duck") is a wing configuration of fixed-wing aircraft in which the forward horizontal surface is smaller than the rearward one, the former sometimes being known as the "canard" or foreplane, while the latter is the main wing. In contrast a conventional aircraft has a small horizontal surface or tailplane behind the main wing."

I can't see how to fit a FOD guard to the canards on my Rookie or my Duck. LOL

Mike

warbirdfanatic

My Feedback: (1)

Grr!! Getting my words wrong again!! Meant to say engine cowl, or nacelle :-)

Justflying1

I do not think that Genuine FOG screens cause a reduction in thrust.