J model props

[gizzard]

It seems to me, from most of the pictures on this site, that the J's are parked with their props feathered. The other models are in, if I remember right, ground idle . Is this to keep the wind from turning the engines, since these props have six and in some cases eight blades and look like a food processor???

Inquiring minds want to know....

Giz

[tinwhistle]

Don't know about that, Giz, but I've noticed that present day crew chiefs move the props (if they position them at all) to the X configuration. The folks in Peoria found it interesting that we old timers positioned the props in the "square" (or is that what you mean by "ground idle") position and that a prop that was in the X position was a "red X" indication.

Time marches on......

Chris

Edited February 15, 2013 by tinwhistle

[gizzard]

Naw. I was referring to the pitch angle of the blade. Dunno about other loadies, I doubt if I am the exception, but my primary instructor at Langley had me learn to do a pre-flight with an FE and a crew chief, just in case it would, some day, come to pass that I would need to do that. Sure 'nough did, several times and every time the FE was surprised that I knew what to do and what I was doin'. anyway, I remember that the FE would change the prop pitches and I would watch and feel the change of position, , ground idle, flight idle, there was a hesitation point in there somewhere. and then reverse and feather.. I don't exactly remember the sequence, but I think they were the positions. after all it has been forty years......One thing Tsgt taught me, by the way, was when ya checked the pitot tubes heat, use the back of your hand and do it quickly, that way you won't be as likely to get a disabling burn on the palm of your hand....years later I would put this to use in firefighting and instruction.............

[US Herk]

We always parked them in a cross and uncrossed them when they unplugged the intakes prior to flight.

I don't think the J prop is connected to the engine directly like the classics are, so that may be way they are feathered - I hadn't noticed (don't see many - yet)

I'm sure a J guy will be on shortly and correct us.

[gizzard]

I can remember our planes havin' the props in both positions, sometimes, and I suspect that it was simply because they hadn't been parked long enough, in whatever position they stopped rotation in.

[C130Hcc]

We always "T"ed the props with the #3 blade down. There is a weep hole there that can drain in that position.

When we did the preflight to get it ready to fly we "X"ed the prop when we took out the plugs.

[SEFEGeorge]

Not sure of the "exact" reason anymore but if you'll notice there are a lot of birds that do that as well. Especially among the bug smashers. I think it has to do with losing oil pressure. Oil pressure on start is what brings it out of feather. Lose the oil pressure and the prop goes to feather.

[BobWoods]

I recall the postion of the prop blades were used by the crew chief to indicate if the bird was in commision or not

[donwon]

On the "A,s" we had one blade in the 9:00 position so the prop oil fill plug would be up where we could check the oil levle.

The blades were in ground Idle.

[Lkuest]

I read up on the J prop a bit, but there isn't a reason explicitly stated in the maintenance manuals as to why the propeller feathers during shutdown other than that's what the computer tells the propeller to do. You can shut down with the blades in flat pitch, but that's the exception, not the rule. There is no prop brake (may be a TCTO in the works), and the propeller is not connected to the compressor, so when the propeller rotates, it only spins the aft turbine (twin spool design).

I believe the intention of parking the prop in feather is to prevent or limit rotation when the aircraft is shut down, and to wind down the propeller more quickly during shutdown. It doesn't work 100% though. I've done quite a few e-model engine runs in front of the J's and got their props to wind up a bit. I also got a kick out of driving by the J maintainers and tell them the forgot to asterisk their props.

This weephole on the E/H prop is largely misunderstood. If it leaked out, you'd have to wonder where the fluid comes from, and why it doesn't all leak out from centrifugal force during prop rotation. You put #1 blade up to prevent the hollow beta feedback shaft (blade angle indication) in the #1 blade area from draining the barrel assembly into the atmospheric sump. That by itself isn't an issue because it all scavenges up during operation. The problem is, when the atmospheric sump gets a sizeable amount of fluid above a certain level just sitting there, gravity pressure pushes down on the fluid to leak out of the front and rear lip seals. The lip seals are just dust covers not designed to hold back anything more than atmospheric pressure. They are garloc seals. We leak check them at 3 psi.

Your mileage may vary though. I was sent out to do a prop service check on an aircraft that was sitting still for 20 days. #1 was pointing down on 2 props, and neither had any evidence of external leakage. They had pretty good lip seals.

Gizzard, I know what you mean about using the back of your hand on the Pitot tubes instead of your palms. I did that with gloves on one time, and instantly smoke poured from my glove. I was taught the backhand method before, and instantly grateful of the advice. I tried to run up to the flight deck to save the pitot tubes and I caught the FE in the way with all his bags in his hands about do come down the steps. The best excuse he could come up with for the pitots being left on was that he hadn't finished his checklist yet. I wasn't even asking for an excuse. I was just asking him to turn them off. Repeatedly. I was contemplating having to use the backhand method again, but he finally managed to put his gear down and flip the switches off.

[gizzard]

I recall the postion of the prop blades were used by the crew chief to indicate if the bird was in commision or not

I think maybe I recall that, Bob, but we never parked the bird in feather, unless, of course, we had a sick fan.......You know how my mind wanders sometimes, off on strange tangents

[SEFEGeorge]

When I did pre-flights I told the CC when I turned the pitot tube heat on. Most CCs were already at them or getting there.

"Pitot heat on now."

[gizzard]

We had a troop, ECS guy, workin' on a stand or somethin' I don't remember now, even why, but they were doin' somethin with the pitot heat. and he checked it by layin' his cheek on it!!!!!!!!!!! Nice burn.. musta had a big bowl of dumbass for brerakfast that morning. I did not see it, my trailer mate Larry Seeders was there and told me about it. saw the guy though...... and this guy worked on airconditioning and pressurizations systems and such???? OMG!!!!!!!!

[BDizzle]

We put the 54H60 prop with #1 blade pointing up for the reason above, the beta feedback shaft and fluid transfer. We 'X' the props when the plane is ready and the plugs are pulled. Some people say you also move the props to make sure the prop brake isn't siezed but I don't buy that. I just bumped the props enough to get a clear view down the intake.

[Lkuest]

We put the 54H60 prop with #1 blade pointing up for the reason above, the beta feedback shaft and fluid transfer. We 'X' the props when the plane is ready and the plugs are pulled. Some people say you also move the props to make sure the prop brake isn't siezed but I don't buy that. I just bumped the props enough to get a clear view down the intake.

Our T.O. actually tells us to release the prop brake by slightly bumping it. It also tells us to alternately bump the prop and inspect compressor blades for about 30 degrees of prop travel to fully inspect all the inlet compressor blades.

People talk about the beta feedback shaft transfering fluid, but it is largely misunderstood. If the beta feedback shaft transfers fluid when #1 is pointed down, wouldn't that also happen during operation with centrifugal force? The beta shaft allows the barrel to vent air and excess fluid into the atmospheric sump in the pump housing. During operation, the atmospheric sump fluid is scavenged into the pressurized sump. When the prop is static, the atmospheric sump retains that fluid. If the fluid level rises above the bottom level of the front or rear lip seals, gravity puts fluid pressure against the seals. The lip seals are garloc seals, which are pretty much dust covers not designed to take fluid pressure. We leak check brand new ones at 3 psi. This is why lip seals are allowed to leak 1 drop every 45 seconds. Your mileage may vary though. I was dropped off to do a prop service check on an aircraft that had been sitting for 20 days. Two of the props had #1 pointed down the entire time, but there was no evidence of leakage. Good lip seals.

I've heard of Crew Chiefs so afraid of getting an LOR for a low oil light incident, they don't even bother checking the fluid level, they just pour 2 quarts in the prop and call it a day. They don't get threatened with an LOR for overservicing the prop, so why wouldn't they? The problem is that fluid has to go somewhere. Whether the barrel gets full and vents the fluid to the atmospheric sump, or the pressurized sump becomes too full and vents excess pressure into the atmospheric, the bottom line is the fluid level is much higher than what is required to create external leakage throught the lip seals, which creates more work for the jet troops at best, or sends the aircrew to the hospital for smoke inhalation at worst. I think overservicing props on purpose to avoid stress is criminal. LOR's aren't the answer for the low oil light problem. Only proper training is.

The bottom line is leaving #1 blade down causes a leak for the same reason as overservicing does, by raising the atmospheric sump fluid level above the bottom of the lip seals.

[BDizzle]

Our T.O. actually tells us to release the prop brake by slightly bumping it.

Is it possible for the prop brake to lock even if the prop never spins backwards? Since it's supposed to be held disengaged by starter torque anyway I just never understood the worry about bumping the prop by hand before starting engines.

[Lkuest]

Is it possible for the prop brake to lock even if the prop never spins backwards? Since it's supposed to be held disengaged by starter torque anyway I just never understood the worry about bumping the prop by hand before starting engines.

You're on the right track. If you never set the prop brake in the first place, why would you need to release it? I'm not really sure on that one, but you never know who tried to spin the prop backwards between flights while being around the aircraft. Maybe someone on a maintenance stand was leaning on the prop blade, or maybe all the oil that lubricates the brake lining can get squeezed out from the spring tension holding the brake in the applied position. I'm assuming it's been a problem before because it's pretty much step #1 in the FI to check the prop brake if the starter shears. It CAN be set hard enough to shear a starter. We got called for a stuck prop brake, and I bent the T-bar trying to move it. That's when I wisened up and learned you are supposed to pull on the bar, not push. Also, it helps to jam the prop towards in the wrong direction to break the initial friction of the brake wedge, then it should rotate like normal. Sounds counterproductive, but it works wonders. I'm not sure if it came back shut down or not as the blades were already in ground idle.

[combat donkey]

The J prop moves towards feather on shutdown due to counter weights and lack of oil pressure. The prop blades are normally fully feathered on the ground to stop them windmilling in the breeze as the J has a free turbine design. The RAF aircraft are fitted with a prop brake but we still feather just in case.

[larry myers]

Is engine normal ground shutdown on the J like the E/H consist of simply moving the condition lever to ground stop? Is there even a condition lever on the J?

Looking at static J photos I often wondered why the props were always feathered. Now I know. Thanks combat donkey.

The P&W PT6 engine prop also goes to feather on normal shutdown.

[Spectre623]

The #1 blade was parked at 12 oclock to "preclude" oil leakage from the beta feedback shaft. When it is cold this is the fix for that drippy nose prop sometimes. Bill

[combat donkey]

No condition levers on the J all done by the fadec. Just an on/off switch. Turn it off as it shuts down the prop will move towards feather as i said earlier then the prop aux feather pumps or t handles are used to move it to full feather position .

[Steve1300]

The #1 blade was parked at 12 oclock to "preclude" oil leakage from the beta feedback shaft. When it is cold this is the fix for that drippy nose prop sometimes. Bill

Yep, for some who don't understand how the beta feedback shaft lets fluid run through, they need to remove a pump housing one time and watch how much fluid comes out of the unsealed shaft. There is a lot of fluid in that barrel and dome looking for a place to go when the prop is not turning.

When the prop is turning, the scavenge pumps won't let the atmospheric sump fill up. When it is not turning, the levels can rise to the lip seals.

My books tell me that lip seals are not allowed to leak. I don't have a "lip seals can leak one drop every 45 seconds."

[Spectre623]

Gee...I thought that was what rags were for, that and the boost packs and struts and steering cylinders and suction boost pumps, and, and, and... Bill

Edited February 27, 2013 by Spectre623

[Lkuest]

I don't have a "lip seals can leak one drop every 45 seconds."

It's in the 1C-130H-2-61JG-10-1, S/S/SN 61-10-21, para 6 for Propeller leakage inspection. The pump housing as a whole is allowed to leak 1 drop/45 seconds either operating or statically. This does not include the propeller shaft seal, and nothing else on the prop is allowed to leak. If I get called out to an airplane for a lip seal leak, I'm going to use the maintenance book for the limit. If the aircrew refuses the plane for something that's within limits to me, it's their option, but it's also a late or an abort against OPS, not MX.

[larry myers]

If I get called out to an airplane for a lip seal leak, I'm going to use the maintenance book for the limit. If the aircrew refuses the plane for something that's within limits to me, it's their option, but it's also a late or an abort against OPS, not MX.

Oh yea! My kind of talk.