PT6-28 Question

[Go Juice]

Hey there.

Quick question about PT6-28 engine startup. Some seems to put the prop lever FULL FWD as mentionned in the POH and some other ppl like to start them on feather. On a Be10, why would ppl start them at feather against what the poh says? any advantages, oil temps, pressure ect .?


peace!

[Brantford Beech Boy]

nope. should always follow the AFM.

BBB

[tca]

Prop lever position should have no effect on start parameters. The props won't start unfeathering until there is oil pressure, which won't be high enough until after the engine is self sustaining. On early serial numbers, where the oil pressure gauge is AC powered, the props unfeathering is the best way to determine that you have oil pressure without turning the inverter on.

At my company, we usually start with the props in the max RPM/fine pitch setting, and only start in feather if we are doing a gpu start, which makes life easier for the ground crew who has to unplug the gpu!

[402_pilot]

At my company we do this because some of our A100s have DC oil press gauges, while others are AC. Since we dont have our inverters on during engine startup, on the AC oil gauges, we start full-fine and as the prop comes out of feather, we put it back to feather. This confirms positive oil pressure. On the DC gauges we leave it feathered for start.

Alex

[Go Juice]

So why is it that companies create SOP's that don't respect what is in the POH?

The oil pressure check with the prop unfeathering is a good point but why not start it in full fwd regardless of the type of oil pressure gage you got?

As for the GPU start, why not start it Full FWD like the POH states and then put it in feather after it's started?

I have no experience on turbine, just trying to learn a few things..

thanks

[402_pilot]

In our operation we do many gravel strips so our SOP says to keep it feathered as long as possible to avoid picking up gravel and damaging the props.

[co-joe]

That is a Borek-ism.

The reason is that when you start the engines in full fine, the FCU is at the idle stop, but at feather, the FCU is at the min flow stop. At a small company the difference is negligible, but when you have hundreds of engines doing thousands of starts a year the fuel savings is measurable... at least that's the Penekitt-ism as it was told to me.

Could be a lower prop damage thing as well having to do with gravel and standing water. If you start in fine sometimes you have to be real quick going into ground fine to keep from picking up stuff off the ground. In Fx, no problem until you are ready to start moving.

But then someone will say that can cook the side cockpit windows by directing hot exhaust at them... there's arguments both ways, the right one is the one that keeps the peace...

[torquey401]

when you start the engines in full fine, the FCU is at the idle stop, but at feather, the FCU is at the min flow stop

HUH? Please explain that one!

[Les Habitants]

So why is it that companies create SOP's that don't respect what is in the POH?

The oil pressure check with the prop unfeathering is a good point but why not start it in full fwd regardless of the type of oil pressure gage you got?

As for the GPU start, why not start it Full FWD like the POH states and then put it in feather after it's started?

I have no experience on turbine, just trying to learn a few things..

thanks

Because some companies operate airplanes outside of how the designer intended for them to be used. I can promise you Ed Swearingen did not think his Metros would be used on gravel strips when he designed the Metro 2 (landing lights out of the belly behind the nose gear...to name one thing), yet companies like Carson Air, SkyCare, and Perimeter fly them into gravel strips every day.

When an SOP has been developed against manufacturers recommendations, ask your CP. Mention the reference in the POH, and see what his response is. If he says the SOP was made whilst unaware of POH recommendations, than do what the POH says (and have a second thought about who you are working for). If he says he's aware of the SOP but this is what the company does, it's probably because through their experience, they have found the advantages of doing one thing one way (like starting in full feather) outweigh the advantages of doing what the POH says. This is something that would have been throughly thought through, whilst in consultation with maintenance/the manufacturer.

I am NOT suggesting we disregard the POH, but SOPS ARE there for a reason.

[SAR_YQQ]

We used to start our fleet of BE90's in feather for quite some time - less chance of the aircraft running away from the student if he didn't set the brakes - also less prop blast for the very busy ramp here.
We changed our SOPs to reflect the POH after it was pointed out to us by a mechanic that we were ruining our engine nacelles by starting in feather. All the hot gases would be trapped within the cowling near the exhaust stacks causing expansion within to occur - effectively popping rivets and damaging the fit. Once we changed back to following the POH, we noticed less wear and tear on the engine cowlings.

[Meatloaf]

Co-Joe, The prop lever is not connected in any way, shape or form to the FCU. Being in high rpm or feather has zero effect on the N1.

[longjon]

co jo, just what I was going to say, regarding the prop lever vs power lever comment -- next time the maintenance guys have the cowls off go watch the power lever stops and have someone move the prop lever, what do yo usee

sure hope the rest of the Borek pilots are a bit more PT6 savey than the guy who wrote that

[StudentPilot]

Going off topic a little since I don't fly a Beech or behind a -28...

I seem to recall the Twin Otter (-27 engines) says to start in feather (correct me if I'm wrong). From this thread and what I've heard previously, Beech's say to start in full forward. I think Caravans say to start full forward. My plane says start feathered above 10°C or full forward if below 10°C (another -27).

Are the differences in starting procedures WRT prop position due to nacelle/cowling design, engine location, a minor difference between models, or something else? I've asked several people before and never gotten a good answer...mostly do what the POH says. I'm curious why the POH's say what they do, and why it seems to vary amongst small PT6s.

[ODA]

Apparently quite a few people need a PT6 lesson. I’ll let co-joe explain the difference between idle and min flow.

[rigpiggy]

from my recollection the min flow valve is bypassing the fcu, and come into play when there is a break in the p3 line releasing pressure on the pneumatic bellows.

afa the prop below -10 start in fx so you don't blow the prop seals, u can even have somebody hold the prop

[ScudRunner]

Because some companies operate airplanes outside of how the designer intended for them to be used. I can promise you Ed Swearingen did not think his Metros would be used on gravel strips when he designed the Metro 2 (landing lights out of the belly behind the nose gear...to name one thing), yet companies like Carson Air, SkyCare, and Perimeter fly them into gravel strips every day.

.

so where does Carson Air fly Metros into gravel strips everyday?

[KAG]

Starting your pt6 over gravel you want to start in fine. Assuming you swept under the props you will kick up a lot less crap then starting the engines feathered. After the engine is stable place the power lever over the gate and into beta to really fine tune the blade angle to further reduce wear and tear on the props. This is all for naught if you don't sweep well the area behind and ahead of your props.

[The Hammer]

AFM/POH's for these type of aircraft are generally +30-40 years old (when 2 crew was the captain + an F/A at the hotel) with the only changes being made when the FAA waves a very big stick (rare).

You have to use your judgement in many areas ie Electrical smoke/fire- nearly every AFM of this vintage states -once you have extinguished the smoke/fire, attempt to isolate which system caused the smoke/fire, often by pulling all the the cb's and pushing them in one at a time to isolate the circuit.

The knowledge gained from Air Canada in cinncinati, Swiss Air in Peggy's cove, and likely UPS in Dubai have/will pretty much shown that in my opinion unless I am going to die without it, I am not trouble shooting the problem circuit in nearly any circumstance. ie I can pump down gear and land flapless and use a vacuum instrument or peanut gyro, fly nordo, if I have to OR pick the bare minimum systems to get me on the ground. If I am in VMC conditions I will not be entering IMC unless absolutely necessary and I will be landing "AS SOON AS POSSIBLE not "AS SOON AS PRACTICAL"

[meflypretty]

when you start the engines in full fine, the FCU is at the idle stop, but at feather, the FCU is at the min flow stop

HUH? Please explain that one!

Stick to your guns co-joe. I think I'm with you. It's been awhile since I've looked at it, but I remember something about Py air being dumped at the Nf governor when sitting in feather, which would put you at the min flow stop.

[rigpiggy]

no the only connection from the PCU is via an fuel topping governor dumping P3 affecting the pneumatic bellows. The FTG cuts in at 106% of selected prop rpm.

[rigpiggy]

http://www.tsb.gc.ca/eng/rapports-repor ... ndix_A.gif

[co-joe]

If memory serves the idle stop is around 51% N1 on the Pt6 whereas the min flow stop is at 49% depending on atmospheric conditions. It could be afunction of Py and the FCU I really can't remember. I have had the cowls off and seen all the linkages, as far as I'm concerned it's all PFM to me. (pure magic)

[rigpiggy]

Not that i recall, when the P3 started to govern on the -67 FF went up to 200 aside up from 90 whether in FX or full forward. I recall on the -42 it went from about 75-150

[oldtimer]

Every PT6 powered airplane I have ever flown, except the 100 series DHC-6 says start the engines with the prop controls full forward. My suggestion is to follow the AFM.
The AFM is the bible, everything else is just hearsay.

[ahramin]

Here's the history on this:

A long time ago a Twin Otter operator in Canada bought some King Airs and either didn't read the afm or decided not to follow it and applied their Twin Otter experience to operating their King Airs. On some Twin Otters the AFM has you start the engines in feather. I'm not sure why this is but one of the effects it has is as stated, the FCU is at min flow rather than idle. In order to save fuel the GM of this operator decided to use the same procedure on the King Airs without knowing if it had the same effect (he wasn't always sober when making decisions).

However, in all PT-6 King Air aircraft there is NO connection between the prop lever and the FCU. It has no effect on the fuel flow. The operator in question did manage to melt a side window through this procedure and at that point decided to follow the AFM in warm weather.

As for not following the AFM in old airplanes, it is a valid point but must done with a great deal of expertise, research, caution, and forethought. In this case however, King Airs are STILL in production and they STILL start them in fine. There are though, a few things to be learned about flying old King Airs from looking at the new AFMs.