Tips & Techniques: PT6 Engine Start

[@cyberrasputen1718]

Thanks for the walkthrough ! I’m in school finishing up my A&P mechanic certification. Our project tomorrow is starting and monitoring the PT6-20 engine. Of course we have inspections too, but this was helpful. We’ve ran through all the slides, but it was really nice to get a look inside at the controls and gauges in advance and get an idea of the layout. I appreciate this very much!

[@ScullBayProductions]

The sound of a turboprop is music to my ears.

[@thomashorne1709]

The start was OK! There are two redlines: one for the start, and another for other operations. The start redline is higher! Look at the ITT gauge carefully. You'll see a small, printed "start" label above the fatter redline. That's the redline you want to observe for starting.

[@bmw_m4255]

you need to look at both redlines, there is a time limit at which you can be above the first one.

[@adrianestrella9539]

Once you're above the first red line you start the timer, not sure what it is in this specific model but mine is 5 seconds.

[@pwayne3580]

The start was disgusting hot!

[@Bartonovich52]

All depends on the engine and the ambient temperatures.. winds, etc. I’ve also found that P&WC are remarkably inconsistent in setting the secondaries in the FCU. Some light off so fast that I wonder if I’m getting a hot start.. some so slow that I wonder if it’s hung.

[@bmw_m4255]

weak battery

[@Wileybird03]

Kinda looked like that was hotter than any PT6 I’ve ever started!

[@aviation3530]

1:58 disengage the starter and let it "spring back" to the off position? Hmm not a whole lot of springing back occurring.

[@Bartonovich52]

It’s not a spring back. It’s a gated switch. You lift it up over the gate and it stays there. I don’t know why they call it a spring back. That’s what the generator switch is. You move it to RESET and let it spring back to ON.

[@kevin3063]

@@Bartonovich52 does the starter cutout automatically at 50%? Then u just move the switch to off?

[@FritzWeinrebe]

@@kevin3063 All manual - no auto cut-out. It is the same on the B1900C.

[@hawx242]

@@Bartonovich52 hey are you familiar or an expert with pt6 engines? I have some questions

[@JasonAirInc]

Very cool. Thanks for posting this.

[@seoceancrosser]

If that was a “cold” engine, it sure looked like a warm start. Is that common with the black hawks?

[@poly_hexamethyl]

2:08 Just wondering....how is the torque measured? Some kind of strain gauge on the prop shaft?

[@bmw_m4255]

it uses a manifold and a transducer which measure oil pressure. that oil pressure transducer is calibrated to the gage in the cockpit with a dead weight tester. But to answer your question it's calculated base on oil pressure. The manifold and transducer is located on the front left hand side of the engine, nearby the prop governor.

[@diegobeatrice5257]

Hi, great explanation! One question from a jet jockey with no experience on turboprops but always fascinated by them! If I understood it correctly while operating in the beta range, the torque maintained at a constant value - either low or high idle based on the setting of the condition lever in a free turbine engine, and u vary the thrust by varying the pitch angle on the blades so that is for instance you move the PL forward you increase the blade angle first increasing the mass of airflow accelerated backwards and thus as a reaction the thrust that propels the aircraft forward, and then the HMU - i assume a sort of bottom governor - increases the ff to the engine to compensate for the increase in the required torque to maintain constant value - low or high idle - to drive the prop and the accessories on the AGB and the RGB, like the generator, for instance; and vice-versa. Also my question is, why do u need a beta range while on the ground? can t u operate the prop and the engine in a normal way as when in the forward thrust regime? Thanks for sharing

[@Bartonovich52]

Alpha is the normal forward thrust regime. It’s limited by the flight low pitch stop in the air and the ground low pitch stop on the ground. These low pitch stops are movable and artificially created by the beta valve which controls oil flow from the prop in combination with the beta feedback ring and the prop solenoid. (This applies to a traditional PT6.. not the Blackhawk shown here). The power lever controls N1 via the FCU input shaft in alpha range. The N1 idle is set by the condition lever and it’s usually left in low except for a cross gen start. N1 correlates with torque as it advances as well as prop RPM until the prop moves off the low pitch stop and into the governing range. Beta is the range below the ground low pitch stop to the start of the reverse range. This is controlled directly by the power lever via the reversing cam which is stationary in the alpha range. The reason you control the prop this way is so you can have quick reacting control of the thrust in this range. Most taxiing is done in Beta which saves brakes so you can set a neutral or a zero thrust or add it or take it away with the lever movement. No prop governing is necessary in this range because N1 remains at idle though all three governors (primary, over speed, and fuel-topping) would become active as necessary if there was a runaway. Reverse range is rearward over another gate and this adds N1 to add reversing power via that same reversing cam as well as moves the prop below the beta range into reverse. Since the prop is accelerating, it needs to be governed. You can’t use the primary governor because when it senses an over speed it will immediately coarsen the blades.. which in reverse means they will actually move to a finer reverse pitch and then to a coarser pitch which would first overspeed the prop and then produce a ton of forward thrust when you don’t want it. So it uses a fuel-topping governor. This is a valve which bleeds Py pressure from the FCU.. making it think it’s at a higher density altitude than it really is, and reduces N1 to the point that the prop stays at 94% (IIRC) selected RPM on the prop lever. If your prop levers aren’t fully forward.. this means you can’t get maximum reverse RPM, and this means you’ll get an annunciation saying Reverse Not Ready when the gear is down but prop levers aren’t full forward.

[@bmw_m4255]

@@Bartonovich52 nice job

[@richie2544]

@@Bartonovich52 Nice work here.

[@22floridacat]

Here you talk about the NG's but the only gauge I see when you bring up watch the NG'S the RPM gauges. What gives?

[@GoldenAura32]

​@@22floridacatNG is the rpm of the engine as a percentage.

[@tonylam9548]

A whole panel full of steam gauges and P and W were the last one to introduce FADEC. You think with a parent company to pave the way, they be the first to have FADEC but instead they sat on their back sides till competition was seen coming on the horizon.(GE !) The industry's piston engines are in the same shape, still stuck in 1930 technology. The only thing not stuck standing still are the cost.

[@calvinnickel9995]

If it wasn’t for the GE Catalyst they probably wouldn’t have FADEC.

[@tonylam9548]

@@calvinnickel9995 Pratt and W US parents did all the R and D work, and could have transferred the tech over anytime 2 decades ago. Fadec, one button start, auto throttle etc. I first read about a small incident few noticed, GE quietly bought the CZ company Walters that made a clone of the PT-6. That was almost a decade ago. A lot of used Walters went into expensive homebuilt.

[@andor8635]

I wonder in A& P school I thought you had to Montereys the EGT gage? Great Video learn a lot. thank you.

[@michaelpinpin5798]

ITT gauge is the closest thing u can get to an EGT gauge

[@bmw_m4255]

it depends on the engine, some have TIT, ITT or EGT. but yes, instead of focusing on N1 as this guy did you should be watching ITT VERY closely.

[@jimhuskyflying]

At 2:19 the temperature is at 880 degrees and the Redline looks to 858 degrees. Was this video meant to show us the dreaded “hot start”? If so, it did a good job.

[@christopherwilson6527]

Jim Jordan look again, further at 1000 up is a black line with “start” next to it

[@bmw_m4255]

when you start the engine there is a time limit you're allowed to go over that first red line, the guy failed to mention it. Most of the time you will never see it go above unless you have a weak battery, or perhaps high ambient temperature and or altitude. Personally I would've aborted that start and got a GPU. He should have at least explained the time limit above the red line and what to do if it happens.

[@saratogapilot6100]

Ahh, I can only dream. I will just have to be content puttering along down here in the piston altitudes.

[@Bartonovich52]

Flightlevels are boring.

[@bmw_m4255]

how much flight time do you have, what are your ratings?

[@stephen-wy3yv]

I try follow your step but now my engine very low power and always flames go on

[@carytaylor1415]

What is he saying @ 1:22 - 1:25? It is difficult to hear what he said here.

[@trogdor2002]

“it’s more of an on/off fuel valve” I think

[@diyfamily6848]

I think you would like to be watching ITT gauge immediately after light off at 13% and be looking for over temp, and secondary peek, rather than down the road at self sustaining 53 % starter off wouldn't you ?

[@ericgirardet1848]

Much easier to start than my R1340 😊

[@potpot1907]

T6 ?

[@ericgirardet1848]

@@potpot1907 Yes 😊

[@potpot1907]

@@ericgirardet1848 Awesome!!

[@ericgirardet1848]

@@potpot1907 you my find my bird on my website: www. T6-Texan.ch

[@potpot1907]

@@ericgirardet1848 i used to study T6 when i am a aircraft mechanic student but unfortunately i never has a chance to run a R1340.

[@cellnot]

What is the SFC in ground idle?

[@cel42334]

I guess no one noticed the start line on the ITT gauge...it wasn't a hot start.

[@bmw_m4255]

i would've aborted that start there's no reason for an engine to start that hot unless he has a weak battery or something else.

[@_multiverse_]

Uh, on the turbo otter I fly in ITT never goes past 700...

[@bmw_m4255]

this guy had a dead battery or something

[@_multiverse_]

@@bmw_m4255 that’s more than likely.

[@mikearakelian6368]

Itt looks hot to me...cool start on my caravan was 700...

[@mikearakelian6368]

Not enough time on start procedures critical part of PT 6 operations...what about max outside temp on hot day?....

[@ebeirne1]

The ITT exceed the red line, wasn’t this a hot start he talked about?

[@daman737]

There is 2 redline one for normal operation and 1 for start

[@beaterstang0898]

Max temp on start is 1090*c

[@bmw_m4255]

if you exceed the first redline during a start you need to make sure it doesn't stay there for long. there is a time limit.

[@747driver3]

It sure didn’t look like the ITT gauge rose slowly and stayed beneath the redline. Better get your resume together.

[@ericbtn4837]

The ITT we can see there is NOT recorded during a start!! All PT6 in the world except A6 and A20 make a stop around 38/ 40% while secondary nozzles start to spray and the TQ gage doesn't stay at zero. . This video is a set of different views to explain what happens during start: That's it.

[@bmw_m4255]

maybe they guy didn't turn on the inverters so the torque gage was inop. I'm sure this was an engine start because if he was temping that high while running that aircraft would be a bucking bronco, and also you can see the altimeter jumping around a bit which suggests the air from the engine starting is blowing back and whipping along the side of the aircraft and hitting the static ports.

[@harryesteves387]

How would you reduce the ITT during start if it was getting too hot? Also, where exactly are the ITT reading taken from in the turbines?

[@Bartonovich52]

You cut the fuel off and switch to starter only until your ITT is below 400. To have a _cooler_ start you need to be more proactive. For me.. I point the aircraft into wind, have engine anti-ice off, have good battery voltage or a GPU, crank until 18% N1 or ITT has reduced to below 200C (if it’s a warm engine) before introducing fuel if I’m concerned about starting temperatures.

[@Bartonovich52]

Oh.. and ITT stands for Inter-Turbine Temperature. It’s taken between the compressor turbine and the power turbines.

[@bmw_m4255]

the ITT is taken with probes mounted between the power turbine and the compressor turbine. There is a harness that leads out of the engine called the T5 harness and it goes to the T5 block on the upper forward right hand side of the engine which then the indicator is connected to with a long wiring harness.

[@2xl830]

Not to be nasty too much, but I must have blinked when illustrations and tips came on the air. Should have been an illustration which isn’t on the tube 10,000 times. What about a cross start ? I’ve searched far and wide and can’t find one video.

[@brianr1840]

I wonder how many times the 17yr old girl in California who attempted to steal the King Air watched videos like this to get it started....?

[@carlifrancis31]

Ahhhh... Wasent that a HOT start???

[@daman737]

Nope there is 2 redlines 1 for start & 1 for normal operation

[@beaterstang0898]

Looks warm, but if I’m not mistaken max temp on start is 1090*c

[@Bartonovich52]

We’d treat it as a hot start. Anything above normal redline is immediate cause for cutting fuel that so by the time you do so you haven’t exceeded the start limits.

[@bmw_m4255]

@@Bartonovich52 i would've also aborted that start, usually you don't see anything above 720ish. the guy needed a gpu

[@reefsandrunways]

“Resume gauge”? How about the “find better MX” gauge...?

[@mikeyb8313]

That’s what I’m saying! Why is there always this “it’s the pilots fault.” Mentality.

[@Bartonovich52]

So true. I’ve seen secondaries come in so hot I wonder if they were set at all.

[@bmw_m4255]

@@Bartonovich52 mechanics don't set the point at which secondary's kick in. it's not adjustable.

[@ghostrider-be9ek]

pilots are supposed to abort if ITT gets too hot too fast

[@shootstraight29]

Guess you couldn’t say the correct full name Pete … Pratt and Whitney Canada …..

[@mikeyb8313]

If a hot start ended my days as a turbine pilot for hire,,not sure I wanna work for that outfit anyway.

[@Bartonovich52]

There’s exactly zero reasons for a pilot to allow a hot start to happen. I don’t want a pilot who cooks an engine that now requires a hot section or overhaul “because maintenance”. I want a pilot who pays attention and discontinues the start before it gets expensive and grounds the plane for weeks. Then they can swap out the FCU or replace the nozzles or take out the inlet plug you forgot that’s now hidden behind the anti ice ramp.

[@mikeyb8313]

@@Bartonovich52 as a jet pilot myself,,I can tell you by the time you react and cut the power to the engine you have already done some damage and will require an inspection. That is no reason to fire someone.

[@bmw_m4255]

@@mikeyb8313 you must have a really slow reaction time bro. but yeah if you do hundreds of thousands of dollars in preventable damage, why get fired, right?

[@mikeyb8313]

@@bmw_m4255 Slow reaction time? We aren’t sleeping, but it might take a couple seconds to react to it. That’s enough to cause some damage. Idk about 100s of thousands though. But you clearly sound like the type of management who would suspend a pilot because he turned back to the field due to an issue and then management who probably have never flown before decided it wasn’t serious enough to turn back…am I right?

[@bmw_m4255]

@@mikeyb8313 no I'm not management.

[@pwayne3580]

Title should be how to cook a wore out pt6 on the ramp.

[@bmw_m4255]

lol