P-Navajo

Poopsmith

Poopsmith

Well-Known Member
I may have a chance to fly a P-Navajo for a bit and I have read a wide variety of opinions on the aircraft/engines. Before I jump in, I would like some feedback from someone who has actual operational knowledge. Specifically I would like to gain a better understanding of managing the engines, flight profiles, and mx issues.

Thanks!
 
If I were you, I'd find an active Amflight or Airnet Chieftain pilot on here, they can probably get you the best practices for operating the aircraft, and they have the most up to date data.

As far as general operating considerations go, make sure you stage cool from whatever your cruise power setting is, down to around 20" at 2" of manifold pressure every two minutes. Also consider that if you're stage cooling while descending, you're going to be coming out of cruise like a rocket (comparatively to level cruise speed). Don't be afraid to tell a controller you can't maintain a certain speed. I'd always tell controllers we can go down, or we could slow down and it was their decision on what they needed more; we got vectored around a lot because of this.

Also consider how fast you're moving in the descent. If I remember correctly, you need around 30nm of real estate to go from 9,000' to 2,500' MSL, and that's only going from 26" in cruise power to 18"-20" on approach.
 
jtrain609 said:
As far as general operating considerations go, make sure you stage cool from whatever your cruise power setting is, down to around 20" at 2" of manifold pressure every two minutes.
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So, I take it AmFlight is a believer in the all-mythical shock cooling?

(Sorry for hijacking the thread)
 
Poopsmith said:
thanks jtrain. Maybe Ian has some info.
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Me?

I haven't flown one in about a year and a half so my memory isn't the best on them.

What will you be doing with the plane? Is it for a 135 gig or something else? Will someone train you in it?

Best advice I can give is:

1) Learn the landing gear system well - it's a little goofy.
2) If an engine starts to go you probably forgot to switch tanks.
3) If this is your first turbo charged airplane be careful with applying takeoff power - make sure it's smooth and even so the turbos kick in at the same time.
4) The engines are very hard to start in cold weather. The more fuel you give them, the better.

I'm sure there's more but it's been a while.
 
There's a lot of controversy surrounding shock cooling and whether it is an actual condition rather than a hypothetical.
 
meritflyer said:
There's a lot of controversy surrounding shock cooling and whether it is an actual condition rather than a hypothetical.
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Yeah... my neighbors won't stop arguing about it! ;)

It's only a controversy if you care. The company said an inch of MP per minute, so that's what I did.
 
Thanks Ian, disregard the PM.
It's for a part 91 gig, and I have not decided to do formal training (sim flite) or do local. I am leaning towards formal.
It is not my first turbo, just my first geared engine.
 
meritflyer said:
There's a lot of controversy surrounding shock cooling and whether it is an actual condition rather than a hypothetical.
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While amateurs are debating whether shock cooling exists, the professionals are taking pains to make sure they don't blow up engines.

Believe who you want, it's your engine, and because you only have one of them, your life.
 
1975 Pressurized Navajo PA-31P-425, uses lycomming TIGO-540E1A engines, they are geared. That is where i need info.
 
Holy crap! Don't listen to a word I said, we didn't have geared engines on our planes. Honestly I didn't know Piper hung geared engines on any of their big piston twins.
 
I have a call scheduled with the previous pilot today, hopefully I'll pry some good info out of him. I'll post what I find out.

FYI the P-Navajos, Mojaves, and one of the Cheyenne models had geared engines.
 
PT-A28 at 620hp (Cheyenne 1)

Talked to the previous pilots and here is the info:

50 gph for planning pourposes
Engines are 1200 TBO and do not liked to be idled lower than 800rpm on the ground.

Profiles:
Takeoff - 2400rpm / 44"
Climb - 2000rpm / 40" Vy
Cruise - 1600rpm / 36"-38" (settings per power table)

Stage cool about 1" per 1000ft drop
Good idea to put the approach flaps down, or you'll never slow down. You can put them down at 180. Gear at 150 if you need.

Pattern - 2000rpm 23" or 24"

Annuals are from $6000 to $20,000 depending on what is broken. 60hrs minimum of shop time. Engine remanufacture is around $70K.

Pilots said be smoov on the throttles, this is where most problems occur. has to do with the counter-weights.

Descents are not a big issue, you will be going fast, so more planning ahead. You really can't have the power out most of the way since the higher wing loading requires some power to keep the descent reasonable.

Pretty much it, i'll post more if i missed something.
 
Ah, I see what's happening here.

That's the PT6A-28 engine, which is a turboprop engine. There ain't no gearing on that thing; the PT6 is a free turbine design.
 
jtrain609 said:
Ah, I see what's happening here.

That's the PT6A-28 engine, which is a turboprop engine. There ain't no gearing on that thing; the PT6 is a free turbine design.
Click to expand...

Actually the PT-6 does have reduction gearing for the prop. According to my information the power turbine turns roughly 33,000RPM at takeoff power, whereas the prop is closer to 2,200rpm.
 
The PT-6 is a free turbine; the prop isn't physically connected to the jet engine part of the engine. The Turbine Pilots Flight Manual (is I think the name of the book) that gives a great explanation of this.

Garrett turboprop engines have a gear reduction box in them.
 
EDIT: Ok on a second read through it doesn't do as good of a job as I thought.

When I get home in a few days I'll get out my book and quote you some stuff out of it about the PT6.
 
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