Ag Flying - PT6 Operation
 

Landing a PT6 powered Air Tractor, is it best to avoid reverse thrust as much as possible and let the brakes do the work?

Or Is it ok to use as much Reverse thrust as you want (providing you have ample forward speed)

When do most of you AT Pilots crack the power lever past the gate?..

Any opinions would be appreciated, its something I have been wondering about lately.

Each to their own, personally -

Hardly ever need it.

Use it once in a while to stay current, as the book says, All wheels on the ground, tailwheel locked, surface considerations etc.

Sure others will have variations on the theme:E

I'm happy to use it whenever I need it.
I feel you should only ever use as much power as you need. Braking power included.
My understanding is that when the powerlever is back at the stop it is at the 'Primary Blade Angle'. Forward of the stop is the Alpha range (normal flight). Depressing the button and moving the lever back puts the blades into the beta range. Moving the lever further back the blades remain in Beta and do nothing more than provide increasingly effective drag until you leave Beta and start to go into reverse. You'll know because thats when your TQ/TOT starts to rise. Up until that point you are only in Beta.
You'll find that you can use Beta to regulate your descent if you need it and then if you need to, as Currawong says, when all 3 wheels are planted, the tailwheel is locked, you can pull the thing into reverse. Smoothly of course.
Bear in mind that you will throw up a fair bit of debris if you carry this to a stop so, like the airline guys, get the lever back into Beta as you slow. I use Beta instead of brakes because it saves brakes and doesn't hurt either the engine or the prop.
Like I said the above is my understanding only and may not be completely correct or even best practice.
Would be interested to hear if any body else sees this differently.

I'm with LLD, thats the way I use it.

Don't be in a rush to use it if your not too experienced, either Beta in the air or Beta/reverse on the ground, the rapid decrease in airspeed and loss of rudder effectiveness may catch you unprepared. Just gradually start using a bit when you aren't under pressure and have plenty of room, to see the effects.

What does everyone do with flight/ground idle?

Hey Turboman
Although I know a lot of experienced pilots use ground idle all the time, I use Flight Idle from the time I leave the pad to the time I pull back up on it.
Keeps it simple and if you need more power on approach for a go-around its there sooner. BTW thats what the book calls for.

What I forgot to mention in the last post but is critical is to always check that prop is set to full fine on final so that when you do go for Beta/reverse, you get it. The way the system works, even though the lever is back beyond the gate it won't happen till prop RPM falls below what is selected.

If you panic and pull it too far back because nothing is happening, when your Prop rpm falls below selected it will come on in a big rush. If you're not planted when that happens, the a/c response could be uncontrollable.

I know I haven't explained that near well enough. Anybody care to help me out here?

CAUTION flight idle ground idle.

If jumping into a machine for the first time, they can be rigged quite differently to what you might be used to. So ask the last pilot if he is a ground or flight idle type.

If he is a ground type, and you try to land in flight, you may land long. And vice versa.

Some people have them set up so at a certain point the :mad: drops out of them.

Which we all knew - just in case someone comes across this that did not know. Safety first, you see;)

I'm sure that some pilots do in fact have their aircraft set up to suit their own personalities/ flying styles. Though I can't believe that any engineer worth his pay would tolerate this.
Frankly, I think thats total BS. Theres only one way to set up ANY aircraft and thats 'By the Book'.
Now if you always set the thing to 'flight idle' and the aircraft tends to want to keep going, pull in a little Beta. If not no problem. That way it doesnt matter how a previous pilot set up Ground Idle. Which is no doubt one of the reasons the factory wants us to have the Condition Lever at Flight Idle when we're in Flight Mode.

Agreed. Unfortunately not always the case. At an average 100 hr inspection I doubt any engineer would pick up that someone had tweaked the prop.

But, on the bright side, someone might read this thread and not break something as a result.

What are you doing up this time of night anyway? I'm off before I start to look like this bloke:8

You know flight idle v's groung idle must be one of the most argued points on PT6AG use. For some reason it has become a personal point! Now I may be a bit of an old fart but when I did my Thrush/Airtractor turbo rating, the boss actually didn't leave it up to me at all.
He said, this is the way you wiil fly it and these are the reasons.
After all it is his cheque book isn't it!
I'm taxing the old 386 a bit here but his primary reasons for wanting me to fly it in Flt idle and not to use Grd idle untill I was pretty much stoped were.
1- If your taxying around all over the place in Grd idle just watch what the ITT is doing. The temp will be up and down and all over the place. Yep you will wear out brake pads in this mode probably twice as fast but if it was my PT6 I think I would be happy enough with that. My first PT6 boss was!!
2- Hands up who has been caught on short final with a heep of sink and you give the power leaver a quick nudge and that sinking feeling stops and you just make it over the fence. Phew!!
Well guess what? if you were in Grd idle you've got a bit of fencing to do!! Now a bit of fencing is pretty cheep hey. But whay if its a bit of a tight strip with a hugh craggy old gully at the threshold about 10 feet deep. Not a good position. This hapened to a good mate of mine many years ago and he cleared the gully by 6 inches, I kid you not. He had the thing firewalled and nothing was hapening, he had to pull back and she stalled as it crossed the gullly and there was an almighty dint in the ground where the mains hit. He never flew in Grd idle again.
All food for thought guys.

Would you believe someone experienced told me many years ago to pull it back to ground idle when on final. Not quite sure why he was pushing up into flight idle in the first place if he was going to do that. I have shut down twice pulling into ground idle on the ground. Not something you really want to happen on final. If your going to do anything with that lever in the air push it forward (on final is a good time as they creep back), DON'T pull it back.

Yeah that piece of stainless that acts as the gate on the condition lever is really 'mickey mouse' and should not be relied upon.

For shorter strips, ground idle works better. I always used ground idle all the time, it's slower spooling up but any engine you don't just bang on throttle so treat it like you own it.

As for prop set ups, they come out of the shop and some slow up and some don't. An odd one if you throttle right back will really slow the Aircraft up, it can be usefull if your aware. It has to be a fairly short strip to worry about through the gate.

It's just basic flying really, know how your Aircraft handles. Every Aircraft is different even if they come out of the same jig, just get used to and know the one your flying.

I Agree with the prop setup being different for each aircraft. I have flown PT6 powered aircraft rigged exactly by the book only to discover the settings almost unworkable. So of course it then comes down the the engineer asking the pilot what he wants.. more go, or more slow. The settings then end up being dictated to how the pilot wants it.

However, when it comes to Ground/ flight Idle operation, my rule is, if its moving then it is in flight idle. Ground Idle should be called start Idle.

I agree that each installation varies in its operation both on the ground and once airborne, with particular referance to the approach phase and how much deceleration is achieved with the lever on or near (or through) the gate with the normal prop rpm selected.


My personal preferance with the condition lever is to use gnd idle during taxing as i find it gives greater control over ITT temps during minor power adjustments, usually select FLT idle during pre-landing checks and I agree it's a dangerous practice trying to go-around from GND idle....it's a loooong wait for ot to spool back up!

Whatever our personal differences in operating it, I reckon the PT6 is Gods gift to Ag' aviation.

There's absolutely nothing wrong with operation in ground idle. The ONLY thing that going to flight idle does is reset the fuel controller for idle operation Ng speed. Above idle, the engine doesn't know the difference.

I believe someone mentioned using beta to control descents. Not a good idea.

Personally, I don't use beta or reverse much.

SNS',
So if you're operating at ground idle in an AirTractor you're not complying with the procedures outlined in the Flight Manual. No biggie till you have to explain to the accident investigators why the condition lever was at ground idle.
What are the engineering reasons for avoiding beta or reverse?
Taxiing in Flight Idle and using Beta to control speed has less effect on ITT than taxiing in ground idle and using Alpha. It mightn't sound that great but I haven't had any engineers tell me its bad for the plane.
I happily use beta on late, late finals if I'm a little hot over the fence. It's an asset in the 802 because its such a heavy aircraft (more inertia) and you're better off having a little more rather than less speed on the approach.
My point here is that there is nothing in the Flight Manual to say 'Don't use Beta or Reverse' but it clearly states that Flight Idle should be selected prior to Take-off. So far I haven't heard a convincing argument for anything different.

Look in a Pratt manual, or consider the operation of the fuel controller itself. What are you accomplishing other than resetting the idle fuel? Nothing.

Further, for landing, having a reduced power also reduces the landing distance and allows the airplane to decelerate slower.

If you're going to be using reversing, you're going to have more reverse and beta available if you're in flight idle. However, I seldom if ever use reverse or beta in a single, and therefore have no need for flight idle position on the fuel control.

On other aircraft, such as several different pt6 powered twins, I will select flight idle as I enter the runway. I don't have to push the power up to get the aircraft moving as resetting the fuel controllers and the increased idle speed does that for me. I also have max reverse available to me, quickly, with the controllers reset. Where reverse will be used for takeoff protection or for landing to shorten the distance, then yes, there's an advantage to setting the controller to flight idle.

Otherwise, if you're not going to be using the reverse on the ground on the rollout, or if you're going to use it but not go deep into reverse, then ground idle is much preferred.

I've never heard of an accident investigator faulting a pilot for failure to use flight idle. Ever.

I've known of a few dingbats who came over the gate into the ground range in flight, and one who stacked up an airplane doing that...but there it won't matter if you're in ground idle or flight idle.

I seem to remember a landing accident involving overshooting into various bits of machinery , where the investigation concluded that had flt idle been used the loader driver would not have had to dive out to avoid the oncoming accident.

An approach at ground idle is going to have less idle thrust, and is going to make a shorter landing than an aircraft approaching at flight idle, all else being equal.

Pretty hard to make the case that landing at flight idle, read higher power setting, makes for a shorter landing.

If you're landing on something that short into obstacles, the real fault is failure to leave yourself an out. If you need to land that short and need deep reverse, you're setting yourself up for control issues by blanking out the tail.

Pick something longer on which to land. Think of it this way. You can always land in less distance than you takeoff, loaded. If you have enough room to takeoff with a load, then you certainly don't need heavy reverse and flight idle on an empty approach to landing.

Perhaps better control of the approach and associated airspeed might be the order of the day, rather than trying to use reversing as a crutch to compensate for a bad approach.

Did I suggest that because I haven't seen it it isn't true...of course not. However, I find the idea that an engine suffers damage during taxi from turns when the airframe does not, laughable.

SNS

Could you please explain why you think so?


How can a slower decelerating aircraft possibly have a reduced landing distance??? :\ If you mean't to say 'faster deceleration' your still wrong for a fully reversable PT6.

With a fully reversable propellor, engine speed is independent of forward thrust. Granted, if you never go into Beta or reverse ground idle is going to give you the shortest landings, but I'm sure your car comes with a reverse gear. Do you choose not to use that as well.

Flight idle will give you more control everytime (if you use the rest of the power quadrant like 99.9% of us) and if your doing Ag on marginal strips with 50+ landings a day it is just a smart place to be.

With all due respect you just don't know what your talking about. Don't forget this is an Ag thread.