RFDS Western Australia - modifying PC-12's with 5 blade props

[havick]

Originally Posted by bolthead

I have it on good authority that you can pick the difference in performance. Not necessarily in a good way.

Can you get a refund on your source/authority?

[Guptar]

MT now have a 7 blade prop that is EASA certified.

https://www.mt-propeller.com/en/entw/stcs/pilatus_3.htm

[merlin45]

I've got a small amount of time in the Pc with both props. In my experience the 5 blade has better T/O perf, quieter and marginally better climb perf. They were about the same cruise TAS for a given power setting. Not sure on the scheduled maintenance side of things but we did have some delamination issues with the 5 blade.

[compressor stall]

Originally Posted by rcoight

Really? I’ve got plenty of time behind both props and given the choice I’d take the five-blade every time.

Performance is much better during take-off / climb and it’s also noticeably smoother / less vibration.

Between this and the PC24 threads, you're sure racking up the kills. Keep it up

[rcoight]

Originally Posted by compressor stall

Between this and the PC24 threads, you're sure racking up the kills. Keep it up

It’s all good. The only people I know who don’t like the 5-blade are engineers.

Maybe bolthead’s source is an engineer?

merlin45 is spot on with his/her assessment from the pilot’s perspective.

The first time I flew with the 5-blade was on takeoff from Switzerland to ferry a new one back to Oz.
After 4000 hours behind the 4-blade it felt like a totally different aircraft. There isn’t anything much in it in the cruise, but takeoff / initial climb is noticeably better. Much more thrust. Different sound too. Quite distinctive, but quieter and smoother.

Don’t know why anyone would prefer the old 4-blade, TBH.

[FGD135]

"The new Hartzell propellers are lighter, stronger, require less maintenance, and provide more torque ... "

"Provide more torque". LOL.

[FGD135]

Much more thrust.

Could that have been due to the colder Swiss temperatures, rather than the prop, rcoight? How do you know they provide "much more thrust"?

[Captain Nomad]

What's the snickering for FGD135? There are different cruise torque charts applicable to the 5 blader. I'll give you one guess as to which way the numbers go - might have something to do with the lighter weight...

[FGD135]

I'll give you one guess as to which way the numbers go ...

Higher torque? That could be because the new prop is turning more slowly than the original. What is the new prop RPM compared to the old?

Also, is it the same gearbox?

[rcoight]

Originally Posted by FGD135

Could that have been due to the colder Swiss temperatures, rather than the prop, rcoight? How do you know they provide "much more thrust"?

No. The temps in Switzerland when I was there were equivalent to or warmer than winter temps where I'm based.
Hard to believe, but it wasn't a non-stop flight Switzerland to Oz. During that trip I also departed from Egypt / Dubai / Myanmar / Delhi / KL all with temps around 40C or above. Noticeably better take-off / climb performance every time.

Since then I've flown around 1000 hours behind the 5-blade, as well as another 1000 behind the 4-blade. Sometimes on the same day.
No comparison. The 5-blade produces superior performance (except in cruise), and is quieter and smoother.

The comment "much more thrust" is a seat of the pants feeling backed up by actual performance numbers.
I would have thought that was obvious.

The 5-blade turns at the same 1700rpm in all phases of flight as the 4-blade, BTW.

[Capn Rex Havoc]

Perhaps the aerodynamics of the the blades produce more thrust than the conventional blades. Blade shape would affect thrust. Thats how you get more thrust out of the new prop.

[megan]

The enhanced performance seen with the new prop is not unusual, it's the exact same reason that other aircraft that have been given the same treatment, even your humble GA piston.

https://www.emerald.com/insight/cont....015/full/html

[rcoight]

Originally Posted by megan

The enhanced performance seen with the new prop is not unusual, it's the exact same reason that other aircraft that have been given the same treatment, even your humble GA piston.

https://www.emerald.com/insight/cont....015/full/html

Exactly. It's hardly a new thing.

Replacing one prop with another with more blades to enhance take-off and climb performance and reduce noise / vibration has been going on for decades.

[FGD135]

Thanks, rcoight.

The 5-blade produces superior performance (except in cruise) ...

Please elaborate on how the cruise performance is not superior to the original prop.

Are you referring to cruise scenarios where the engine power is set at a torque limit, an ITT limit, or neither? If a TQ limit, are these limits increased or decreased, compared to the original prop? If using a recommended cruise power setting (neither a TQ nor ITT limit), then how does the TQ value compare to the original?

Did the AFM get new tables for takeoff performance? Climb performance? Cruise performance?

Apologies for the large number of questions.

Thanks again.

[megan]

Don't know the science behind it, but the new props certified for a whole range of aircraft always improve the take off and climb performance but not the cruise.

[Sunfish]

Thrust reduces with airspeed. That might have something to do with it.

[Global Aviator]

I’m disappointed that no one agrees with me that the ascetics of more props is certainly a good reason!

Ok, that only my opinion.

Think my first love of more props was when I first saw the Panther Chieftain!

[Capt Fathom]

I doubt aesthetics come into it when the accountants get involved!

[rcoight]

Originally Posted by Global Aviator

I’m disappointed that no one agrees with me that the ascetics of more props is certainly a good reason!

I certainly agree. 5-blade prop looks nicer.

FGD135 You’ve given me a fair bit of homework. I’ll answer soon, unless others want to pipe up with the answers first.

I don’t have an engineering bone in my body so can only answer from my own experience flying the relevant aircraft.
The five-blade may be worth a few knots in the cruise (not sure what the FM claims without checking), but if it is it’s barely noticeable.
The highest cruise TAS I’ve ever seen in a -12 was with the 5-blade, but I’m not convinced other variables weren’t more at play than the prop.

However, the takeoff and climb performance is unquestionably better with the 5-blade.

[Checkboard]

Think my first love of more props was when I first saw the Panther Chieftain!