CH-46A APP

As I recall, the units on a 46 were actually refered to as APP's (auxillary power plants). The units on H-34's were APU's. The APP was a small turbine engine located in the rear of the aft pylon, just above the fuselage (rear cabin). The APP was an electrically actuated, hydraulic started unit. In other words, a release of hydraulic pressure would turn the unit, which would ignite at a predetermined RPM ( I can't remember what % of turbine speed that was). One of the worst sounds was the APP winding down after a failed attempt to start it up. That meant working up a full sweat by hand pumping a hydraulic accumulator to get enough pressure to attempt another start. the APP powered a generator and hydraulic pump which would allow the aircraft to be powered up, but did not provide electrical and/or hydraulic power to all systems. How's that for not having touched an APP for 37 years?

Tim Bastyr

Ready APP!

Pretty good Tim! We had to watch the temp as we lit the APP off, if all was okay we let it run. Never did have one over temp, or ever hear of one. Once the engines were up and the blades were turning, the electrical system was on line, we would then shut down the APP and run on generator power from then on. When we were completing a mission and taxiing back into the revetment, or parking spot we'd fire the APP back up to complete the shut down procedures, fold blades if needed etc. They were pretty tough old deals. Hope this helps.
Semper Fi
Joe

APP

"Ready Ape"?

....how many times did we ask each other that question?

Moon

APP

Thanks for the response -

Are you by any chance the same Moon Mullins that flew for
Detroit's Finest?

New Life for the Old Primate

APPs are now being refurbished and used to power homebuilt helicopters. There's a conversion for the Rotorway and the Helicycle comes standard with one. Also, Solar Turbines is located on the approach to Lindbergh Field in San Diego.

The APU in an H-34 was a Homelite chainsaw motor and a motor/generator as I remember. Talk about high tech.

T62 turbine

I figure the CH46 probably had the same t62 as was in the CH53. It was started by the hydraulic charge & had the pump handle in case you lost the first charge . It ran the acessary GB for electrical & hydraulics. I was just reading in the Feb 04 Kitplane magazine where the T62T32 is being inastalled in the RotorWay 2 place helicopter . It produces 180 HP and they said it was originally ordered by the Gov for a proposed two place helicopter. SF PM

Rhat awful wind down sound and that meant pimp back to I think 2500psi about 54 pumps if memory recalls. Most sqds maint guys said if it works leaveit alone or it will break.

Tom would Detroit's finiest be Hmm-768 at Selfridge aaafb/angb?

Wayne, I'm surprised that the H-34 APU engine was a Homelight chainsaw engine. You can usually start those chainsaws. Can you remember trying to start the APU with a pull cord? You are right, real high tech.

APU trivia: What was the intended function of the APU?

Tim Bastyr

APP - Natops Manual

Attached is the entry in the Natops Manual. The next post shows the circuit diagrams for the hydraulics and the AC power.

The APP itself was pretty reliable. The only failure I remember was at Camp Vandegrift and of course, it was late in the day. The power turbine rotor, which looked like a small impellor attached to the shaft and held on by a nut, departed, never to be seen again. Vandegrift was not a place one wanted to RON. There were, of course, no spare units and the first thought was to take a known good unit from another airplane and install it in place of the failed APP. But there really wasn't enough time to do that in daylight and working up on the aft pylon with lights was not an attractive thought.

So I took a look at the hydraulic circuit diagram in the maintenance manal and concluded that if we hooked up a ground cart there should be enough pressure to start the engines. (Hydraulics was my engineering field so I hoped I knew enough to stick my neck out. But this is not necceesarily true). Anyway, we got a ground cart, tied it down in the back of an H-46 and took off for Vandegrift. We did have the sense to test the ground cart and make sure it ran OK. Half way there, when I'd calmed down from persuading the maintenance officer, the CO and most important, the NCOiC, Hydraulics that using a ground cart was feasible, I realised that we should have tried it on an airplane at Marble. Well, too late now. It was getting dusk at Vandegrift when we arrived, hooked up the ground cart, ran it flat out and started up the engine. My heart nearly stopped when the engine RPM seemed to hang up (I noticed later they did that but it seemed like 10 minutes instead of the second or so). Then it took off and fired up OK. Of course, I knew it would all the time. Right!! Hero instead of Goat. For a short while anyhow.

Circuit diagrams from Natops Manual

These diagrams go with my other post

APP

Tim Bastyr is right the APP was hyd. started by the APP motor pump. Best started if the accum. had 3000 psi, which went through the app start valve. A bad start valve would let the accum. leak down to the 1500psi precharge. They would leak often and were a pain in the butt to change! That's where your bubble chasers got the pink tee shirts from. It was the 1st rags job to pump it up. A good bubble chaser could get one started with no hyd. press. we were fast pumpers! Finding leaks onboard ship at night was a tough job with a red flashlight. What a job!
Semper Fi,
Tim McMahon HMM-262 hyd. 65-67

Part of the preflight was ensuring there was sufficient pressure in the system for APP start. If you had a no start the pilot who checked the pressure assumed responsibility for pumping the pressure up for the next start.

"Ready APE..."

I'm surprised that nobody has yet to mention what happens:

a) when the "FNG" copilot would hit the APP start switch BEFORE asking the Crew Chief if the APP had enough pressure to start the "APE"....

b) when the FNG copilot would hit the start switch and accidentally switch it back off....

c) Switch it on then off again when he realized that the pilot had not yet given the order to "Start APE"....

In any case, the Crew Chief had to scamble from where ever he was to get to the APP pump handle, before the pressure was drained off, pump his guts out to get the hydrualic pressure back up to an acceptable level which would produce enough revolutions to fire it off and flop on the aft ramp completely exhausted.

However,bug-eyed, sweat pouring down out of his helmet, arm hurting like Hell from the over-exertion, chest wheezing like an old accordian, just barely enough oxygen to survive, a good Crew Chief ALWAYS had enough breath ledft in him to utter:

"...!@*#$%^& -- FNG!..."

Aaaaahhhh, sweet memories of youth - those were the days.!!!

Tim,
I'll have a try at your trivia question. They were installed for running the heater without having to run the engine. The cold weather kit had a lot of ducting and covers. With 24 helicopters it was a real storage problem for something that was never used.
S/F
Ernie Needham

APP stuff!

John Dulligan is the "King" of CH-46 knowledge, no question about it! Hand him the crown now, don't waste any more time! Great post and info, John! Thanks for your input.
Semper Fi
Joe:rolleyes:

John Dullighan

Joe

John better have his collective stuff in one bag. He was a Boeing Tech Rep on that bird. I hope he knows what in the h*** he is talking about!!!! Met John at the San Diego airport on his way to his first Popasmoke Reunion. He had a great time and contributes to a lot of different forums. I, for one, am glad he found us!!!

SF John

Larry

Crown Prince

Thanks Joe but Norm Clark is King and Emperor in my book. I'll take Crown Prince if only because I can read.

When I left Boeing my boss, Jack Geier commented that Tech Reps coming in from the field passed through a zone where stuff was stolen - but only thngs like Natops Manuals, Company reports and flight gear which seemed to reappear later when the guy had left the company.

Ps: "Ready Ape" has nothing to do with the appearance of the crew chief.

H-34 APU Trivia Question

Ernie Needham wins the trivia question prize! Gee Ernie, I didn't think that anyone would remember that the intended purpose of the UH-34 APU was to run the heater. For those that lack your exceptional memory, the purpose of running the heater was to pre-heat the engine and transmission in cold weather.

I cannot remember ever actually using the APU for that purpose. In fact, the only time I ever saw the APU used was to start the engine in the case of a low battery charge. That really took some tinkering to accomplish. Every time the pilot cranked the engine, the APU would stall.

S/F
Tim Bastyr

Tech Rep

Larry,
He was our Tech Rep in HMM-165 when I was there in 1967-68! I know from where I speak. King or Crown Prince, he can fly with me anytime he wants, any seat he wants!
Semper Fi
Joe

Tim,

Thanks for the grand prize. I never saw the ducting used either. I do recall when I was a member of HMR-362 and we took our HUS-1 (H-34s) out to Oppama in 1959 aboard the USNS Core.
The R&T (Repair and Transfer) group at North Island did install all the covers. Which were blue by the way. They didn't match the Marine green very well.

S/F
Ernie Needham

Cheap Oppoma Marines now that brings back memories.

Hi Walt,

Yes, lots of fond memoires also of Oppama. Without doubt I think it had the best mess of any I ever attended. HMR-362 was the second squadron to take the HUS-1 to the Far East. I think 262 was first. When we arrived in May 1959. HMR- 262 was in Korea on maneuvers. When they returned it got very crowded with that many birds parked in such a limited space. As I recall most of the helicopters had to have blades folded. That was okay, good practice for the ship. HMR-262 soon departed for Okie. We, along with a few remaining members of the MAG departed Oppama in March of 1960 aboard the USS Princeton. Sad day indeed.

S/F
Ernie Needham

Needham. E, AES-41

Ernie talked before about your father & uncle being in the Corps. I have a group photo of AES-41 back in late 40ies with picture of E. Needham CWO expect that was your father. Do you have this ? If not will have a copy made & send it if you give me a mail address. I remember well the App on the UH34 and the rope a dope to get it started. Also as to the heater in hot weather the sensor would automatically start the fan in the heater. As for 1820-84c engine changes we at VNAF averaged engine changes at 200 hours or less. Mostly from panic overspeeds or overboosts. When you were being shot at the trottle advanced immediately!!! On filters or EAPs dont know if you were on the CH53 but the EAPs doors were closed until take off when you reached 60 Knots a sensor closed and opened the EAPs doors. I chased down a problem where at 60 Knots the helicpoter jumped and the hyd systems dropped momentarily. This happened for years & all kinds of theories didnt solve it. But I finally found only one thing was common to both Generaters . That was the common ground on the transmission deck. The cause was the EAPs doors drew the highest Volt/Amp load of anything on the Helicopter. Had the maintenace folks pull the ground bracket & found that it had been installed on all CH53 as a dissillar medal installation VS a ground base. Result was the AF change where they were cleaned of the insulation material & bolted VS rivit to the transmission deck. Enough already!! Semper Fi PM

Ernie it was 261 and that was my first helicopter squadron. Sf Walt