Twin Otter Beta Use in Flight

[SuperchargedRS]

In with supplies out empty wasn't that bad.. one way strips so the wind would have to be just right anyone thats flown a pc12 knows that it likes to float so when going around is not an option sometimes beta has to get used.

Heres to hoping you're just a BSer.

And they don't float if you use the AOAs and those nice trailing link gear, those numbers I posted were for a dry hard surface, going in and out of 1k of dirt, I'd think someone smart enough to afford a PC-12 would also be smart enough to not permit their pilots to do something that stupid.

If anything goes wrong operating that pilatus out of a 1k dirt strip, between TC, the insurance company and the lawyers, you'll be eviscerated

[StudentPilot]

How much time do you have as PIC in the PC-12??

Sorry, but even if he left damn near empty and super light on fuel, 1k worth of dirt is most likely BS at best, and very reckless at worst.

I have no time in PC12s.

I don't need any time on type to consult an app or performance charts.

I have not disputed your argument, I merely called you out on bringing an irrelevant 1000 lb under gross weight take off into a discussion about landing at that weight.

Coming out empty at 7,000 lbs has a slightly lower ground roll than landing at 9,000 lbs work according to the AFM Google found. A lot was left out: elevation, temperature, slope, surface, etc that was not mentioned - and how much better maximum braking is over 'average braking technique' that the landing charts use. If it was -20°C the numbers are quite reasonable with a 15% addition for not behind asphalt. If it was 20°C the numbers do not look good.

As for beta in flight, no thanks.

[SuperchargedRS]

How much time do you have as PIC in the PC-12??

Sorry, but even if he left damn near empty and super light on fuel, 1k worth of dirt is most likely BS at best, and very reckless at worst.

I have no time in PC12s.

I don't need any time on type to consult an app or performance charts.

I have not disputed your argument, I merely called you out on bringing an irrelevant 1000 lb under gross weight take off into a discussion about landing at that weight.

Coming out empty at 7,000 lbs has a slightly lower ground roll than landing at 9,000 lbs work according to the AFM Google found. A lot was left out: elevation, temperature, slope, surface, etc that was not mentioned - and how much better maximum braking is over 'average braking technique' that the landing charts use. If it was -20°C the numbers are quite reasonable with a 15% addition for not behind asphalt. If it was 20°C the numbers do not look good.

As for beta in flight, no thanks.

You're right, who need experience or facts lol

Dude are you even a pilot?


Also how far is that 7,000lb PC12 going to fly?

Our is pretty light, only has two seats in the back, and it's not even 7000lbs with Z E R O fuel.

Maybe you should have some experience or training on type before you start trying to correct people who have time in type.





Also, EVEN if you somehow got that plane to take off at 7,000lbs you have just enough ground roll, but your total takeoff distance and also accelerate/stop distance is well over 1,000' and that's on dry pavement.

So again, taking a PC-12 into a 1000' dirt mining strip is stupid all day long and twice on Sunday's.

[StudentPilot]

You're right, who need experience or facts lol

"Facts" like saying it is BS because there is no way he could depart a 1,000' strip at 8900 lbs, which was never stated in the first place?

I would definitely want some experience and to be comfortable in type before making a go/no-go decision, as well as having all of the details, but you broke out the AFM performance data and, in some situations, it does work.

Also how far is that 7,000lb PC12 going to fly?

Our is pretty light, only has two seats in the back, and it's not even 7000lbs with Z E R O fuel.

That may well be. I saw a BEW of 6250 lbs on the preview screenshots for the PC12 digital AFM. I weigh 150. This site says a PC12 burns 26% more than a Caravan. We block a hair under 350 lbs/hr reliably, so 441 pounds for a PC12 approximately. 500 pounds will be ~0.6 hours plus 0.5 hours reserve, I doubt there is an IFR approach so no need for IFR reserves. Not far, although a PC12 does come and go in my neck of the woods flying legs that short regularly.

6250+150+500=6,900 lbs

Close enough for me, for these purposes.

Also, EVEN if you somehow got that plane to take off at 7,000lbs you have just enough ground roll, but your total takeoff distance and also accelerate/stop distance is well over 1,000' and that's on dry pavement.

Total takeoff distance may or may not matter. Perhaps there are 100' trees at the far end of the strip, in which case you may not want to go even if the total takeoff distance is long enough. Perhaps it is a cliff 100' above the ocean and you just need to be airborne by the end of the strip.

As a 703 aircraft there is no requirement for accelerate/stop distance. From my experience, if you can meet the accelerate/stop distance for a given type it isn't a short strip to begin with. No, that does not make it reckless or stupid, merely a short field.

[SuperchargedRS]

That AFM isn't really set all the way up on my phone the pilatus app is great for somethings, but W&Bs ain't one of them, however our plane, which only has two rear seats and a stretcher, is just shy of 6900lbs with zero fuel and zero people.

As for fuel burn, below 10k we plan on 500lbs hr at 240kts.




Now here's the kicker, it's not just legal, that hardly gets you on the bus, it's what's safe and prudent.

Going taking that PCL aft of the gate while in the air, that's not legal, it's not very safe and it's sure as heck not prudent, thus no bueno

I fly this plane all over, we get called to go to airports I've never heard of at times, and the PC-12 is a champ, most anything on a chart and many backcountry strips are no problem for this very capabible airframe.

That said, though I don't legally need accelerate and stop distance, I would be a damn fool not to have it, especially in something like the PC-12 where's it's both a large and fast plane, and also a plane where it's really not asking much realestate to get you that accelerate/stop distance.

Now I'm not flying rich folks, or chips and pop, I do some rather emergent flying, our company also has some pretty high mins to fly here, well beyond ATP, and I don't know a single pilot in the company who would take one of our PC12s into a 1000' dirt strip.

Even if you follow the letter of the law, if you knowingly do something that's not safe or prudent, you will find no shelter from the fall out if things go sideways, and that's only presuming you survive to deal with it.

[Noo]

I remember when I flew a PC-12 for my first job and thought it was a large and fast plane too.

[SuperchargedRS]

I remember when I flew a PC-12 for my first job and thought it was a large and fast plane too.

Far from a first job lol, but for where a PC-12 can land, it's quite quick and quite large

[napoleandynamite]

1000foot unprepared mine camp strips

That's impressive!!!! Did the the phonebook you sit on to see over the dash slide out from under you stopping that quickly?

[shimmydampner]

In with supplies out empty wasn't that bad.. one way strips so the wind would have to be just right anyone thats flown a pc12 knows that it likes to float so when going around is not an option sometimes beta has to get used.

I've heard people say it before, about types that I've flown, but I don't really buy that aircraft "like to float" because of the type they are. I think floating happens when an approach is flown too fast and the aircraft is carrying too much kinetic energy. However, I'm unfamiliar with the PC-12. I believe that it is a very capable aircraft. Regardless, it definitely doesn't seem like the type that would be wise to take in to a one-way in/one-way out 1000' strip. Then again, I've probably done similarly unwise things in aircraft that might not have been best suited for the job, so who am I to say. Where was this strip at, out of curiosity?

Edited to add:
Isn't there a stick shaker/pusher in the PC-12? Would you turn it off for these approaches? Seems like a bad bit of technology to have when doing serious STOL work. I'm very intrigued about this operation now.

[SuperchargedRS]

In with supplies out empty wasn't that bad.. one way strips so the wind would have to be just right anyone thats flown a pc12 knows that it likes to float so when going around is not an option sometimes beta has to get used.

I've heard people say it before, about types that I've flown, but I don't really buy that aircraft "like to float" because of the type they are. I think floating happens when an approach is flown too fast and the aircraft is carrying too much kinetic energy. However, I'm unfamiliar with the PC-12. I believe that it is a very capable aircraft. Regardless, it definitely doesn't seem like the type that would be wise to take in to a one-way in/one-way out 1000' strip. Then again, I've probably done similarly unwise things in aircraft that might not have been best suited for the job, so who am I to say. Where was this strip at, out of curiosity?

Edited to add:
Isn't there a stick shaker/pusher in the PC-12? Would you turn it off for these approaches? Seems like a bad bit of technology to have when doing serious STOL work. I'm very intrigued about this operation now.

That's why I said too fast and too large for that type of strip, though it's not a 747, it's also sure as heck not a PA18.

The PC-12 has a shaker and pusher, there is a button by the pilots left thumb, that if depressed will deactivate the shaker and pusher while the button is held down, this however was NOT designed to be used as an aid to short field work, the plane has quite a nasty stall with full flaps, looks almost like a wing over.

https://m.youtube.com/watch?v=VNRK2aUmWWI

[Victory]

In the related videos there is one taking off and landing on turf in what looks like just a few hundred feet. This aircraft obviously has a very low stall speed. https://www.youtube.com/watch?v=ZP-9mWqFh3c

[bald seagull]

A lot of PC-12 discussion in a thread about Twin Otters.....

AND, not many who understand the term 'beta'.....except GH

[Cliff Jumper]

not many who understand the term 'beta'.....except GH

Or perhaps a chance that you don't.

It's a long debated topic, but my stance is that there are different meanings depending on what you're talking about.

Beta range of the power lever is any position below flight idle.

Beta range of the propeller (in my opinion) is any pitch below the low pitch stops.

[goingnowherefast]

My Twin Otter Flight Safety book defines Beta range slightly differently than my King Air book. I have no idea how Pilatus defines beta, and I don't care as this is a twin otter thread.

[SuperchargedRS]

My Twin Otter Flight Safety book defines Beta range slightly differently than my King Air book. I have no idea how Pilatus defines beta, and I don't care as this is a twin otter thread.

Forest through the trees much?

[PilotDAR]

The key to "beta use" lies in what the pilot is commanding the propeller governor to do. The governor may be governing when the prop levers are pulled back to less than maximum RPM (depending upon the power selected with the power levers). If the governor is governing, the prop is not in beta range. If the prop levers are fully forward, and the power levers back, the blade angle may be moving into beta, or at that phase, disking. When disking, the engines really are not developing much power, so the effect is minor = permitted in flight, but the pilot has not passed the gates with the power levers.

"Using beta" implies that the pilot has passed the power lever gates, and moved the power levers further back, and now two things will be happening: The blade angle will be moving more toward reverse thrust, and the engine power will be increasing. The prop levers remain set to fully fine, even though the blade angle may be moving toward coarse in the reverse direction (governor is not governing), so the power levers are controlling both blade angle and engine power in unison. The pilot will have no doubt that they have made this selection.

I'm not aware of any propeller powered aircraft permitted the use of reverse thrust (behind the gate) in flight. I do recall that the DC-8-63 was permitted reverse on the inboard two engines in flight.

[PanEuropean]

I recently met a pilot who used to fly in Nepal...He said that they had approval to use Beta in flight.

He is incorrect. The type certificate holder (either DH in the early days, or Viking presently) has NEVER granted anyone approval to move the power levers aft of the idle stop in flight.

Use of Beta in flight is prohibited in 2.4.1.1(11) of the -400 POH, engine operating limitations table footnotes. I'm sure its prohibited in the -300 and earlier POH as well.

Absolutely correct. I know its correct, because I'm the guy who wrote the Series 300 & Series 400 flight manuals (at rev 53 and initial issue, respectively), and the FlightSafety DHC-6 training manuals (at rev 2 & 3).

...as I recall on the Twin Otter, 'beta range' is when the propeller rpm is controlled by the power levers, not the propeller levers...

That is correct. A simpler definition would be "whenever the actual propeller RPM is less than the RPM selected with the propeller levers, the propeller is in beta range". But, in the context of this discussion, I think that the original poster was referring to the practice of moving the power levers aft of the idle stop.

...one way they [FlightSafety] teach is if you have a steady beta light you are to power back, feather the prop pull the breaker....then bring it back.

No, that's not correct. FlightSafety teaches students to follow the procedure set out in the AFM, and what you stated is NOT the procedure set out in the AFM. Never was.

...So much easier to just twist the grip if you need a few extra seconds to find the breaker. ...Flight-safety won't instruct for these procedures so we took our own guy and just rented the sim for this training

I find that comment (about your group teaching your own procedures, those being to twist the power lever grip when presented with a steady beta light) a little difficult to believe, because when I was employed by FlightSafety and I did the initial certification of the DHC-6 simulator in 1992, we very deliberately programmed the simulator to freeze if someone twisted the power lever grips when the 'steady beta light' malfunction was active. We did this for the explicit purpose of preventing users (our own staff, or dry rental customers) from teaching unauthorized and unapproved procedures.

There is no need to select beta in flight for that approach with that 2100 foot runway in a Twin Otter. To need to do so it just poor approach planning and speed control.

Absolutely correct. The landing distance for a Twin Otter at maximum landing weight is 1,500 feet (ISA, no wind), and that's without reverse thrust. This assumes you cross the threshold at 50 feet AGL, at 1.3Vs. If you use reverse, the distance will be even shorter.

...not many who understand the term 'beta'.....except GH

Pilots who have a flight test or engineering background will interpret the word 'beta' to mean "propeller operating at a speed less than what is selected with the PROPELLER lever". Twin Otter line pilots generally use the word 'beta' to refer to twisting the power levers and pulling them aft of the idle stop. It would be pedantic to use the engineering definition in a Twin Otter specific discussion, especially when the original poster made it clear he was referring to moving the power levers aft of the idle stop.

Pilot DAR explained things perfectly in his post above. But, obviously, if you are a DAR, you have a pretty strong flight test and engineering background!

Michael
(post edited to correct the typo that fellow forum member Cliff Jumper identified)

[Noo]

I've never seen so many egos murdered by words with one post.

[Cliff Jumper]

Thanks PanEuropean, it's nice to get info from the source.

Your points about 'beta' have me questioning my own understanding. You said the following two things...

"whenever the actual propeller RPM is less than the RPM selected with the propeller levers, the propeller is in beta range"

and

"propeller operating at a speed less than what is selected with the power lever"

My basic understanding of the term 'beta' in general, is any time the propeller is not providing forward thrust. I've understood 'beta range' to be any throttle position below flight idle. However, your two explanations have thrown me.

Your first definition would seem to include flight idle on the ground, where the propeller levers are full, throttles at idle, but prop rpm is less than maximum. I thought in this case there was still marginal forward thrust being produced by the props on the low pitch stops, and therefore not 'beta'.

Your second definition seems to alter this, unless its a typo. Any time you had a high throttle position, but selected a mid-rage propeller setting, this situation would exist, while the governor is governing. Heck even in reverse, how is the prop "operating at a speed less than what is selected with the power lever".??

Can you or DAR clear up this confusion for me?

[pelmet]

Thanks PanEuropean. I knew there was someone on here that was involved with this stuff but couldn't remember the name. I think it changed at some point.

I figured the guy didn't know what he was talking about and I knew you would have the answer.

Glad I followed the recommendations and never did such a thing myself.

Nice to cut through the BS.