AG Flying. Mid field flap extension deemed improper.

[Lowlevldevl]

For those of you with very high boredom thresholds, another excitement charged thread from me:)

Found this while looking for something else and now that I've worked out how to hyperlink, thought you might be interested.
Mid Field Flap Extension deemed Improper (http://www.agairupdate.com/aau/articles/Other/FlapEnglish.html)

[Rarely Dble Amber]

Dont underestimate my boredom threshold LLD :p

In fact that is a good article, recommended reading for any Air Tractor Pilot. For any ag pilot actually.

I have often wondered if there was a measurable difference in the take off roll started with flaps down as opposed to started with flaps up. My feeling is that, like the downwind turn, it is all in the mind. Surely the induced drag from 0 knots to 65 knots is negligable.

[airag3]

Yeah , thought it a bit strange as I'd never heard of that technique but it may just depend upon where and by whom you were taught.

Funny I'd never considered it "Rotating" in an Airtractor either.

[currawong]

Exercise is type specific.

Some there is a gain, some not.

Potential for mis-handling versus gain a big consideration....

[SNS3Guppy]

Interesting article, but appears to have been written by someone who doesn't fly ag, or any other type of utility operation.

While delaying flap application may or may not decrease or even affect takeoff distance, on chips, gravel or any rough surface it may delay or preclude flap damage, especially in aircraft with fabric flaps.

In some aircraft, it's SOP. As a kid in ag trucks, we used a STOL installation, and would only apply flaps when the tail got light. As soon as it did, we went full flaps (with significant aileron droop), and full forward stick. The tail would pop up quickly, we'd go full aft stick and the runway would be behind us.

We also added power and swung the tail while back taxiing at the very end. Some debate the merits of gaining a little coming out of the turn, but I think it helped, vs. a standing start.

[prospector]

Starting the take off run from a turn may have given a few knots airspeed but was very destructive to prop hub due to gyroscopic loadings. It can be a very expensive exercise, both financially and the results of a loss of prop blade in flight. Method was used a lot in early days but very much frowned upon when knowledge of prop damage was discovered.

Prospector

[SNS3Guppy]

Prospector, I'm also an inspector and mechanic, and have never come across any propeller damage from turning on the ground. I would have to call you on that; a normal turn on the ground that isn't going to hurt the airframe is absolutely NOT going to damage the propeller, bearings, journals, seals, or any other part of the airframe. If you're going to see damage from a turn, it's generally going to show up in the landing gear first. Certainly not the propeller.

A turn on the ground is low speed no matter how you slice it, high speed groundloops excepted. But a turn to start the takeoff roll isn't going to be a high speed turn, nor is it going to cause any damage to the propeller whatsoever.

[Lowlevldevl]

SNS',
Take your point about flap damage. However, at least 3 serious hull losses seems to be an expensive alternative to some dented flaps. I always use 10 degrees on take-off, selected on the pad, worked off some serously rocky strips and have never wrecked a flap.
I don't have much time recently in anything other than AT's so can't comment on other types, but if you're an AT pilot I think the report has some real merit.

[prospector]

SNS3Guppy,

The practice of loading and then taxiing to the end of the strip, adding copious amounts of power whilst carrying out a sharp 180 degree turn was believed to be the cause of propellor blade shedding accidents in the NZ ag industry.

I can recall getting a memo from the chief engineer to all company pilots to cease and desist from this practice. The chief engineer was responsible for some 30 aircraft at this time, and the results of these 180 turns, on the ground, feeding in large inputs of power just to pick up a few knots at the commencement of the T/O run was proving to be an expensive exercise.

I must admit I did not strip any of these propellors myself and examine them, but the engineers certainly had plenty to work on to form their opinions. The practice was also very tough on the front crankshaft bearing, also due to gyroscopic loading.

Prospector

[SNS3Guppy]

Sounds to me like someone was looking for pilot caused damage, and lacking anybody talking, that was the culprit. I've never seen an engine of any kind damaged by turning on the ground, and I'll bet you dollars for donuts if the gear isn't damaged, then there's no way you're going to see any kind of perceptible damage from "gyroscopic forces" on the ground.

I've never seen it in any kind of engine, from a lowly A-65 to IO-520's, to R-985's and R-1340's, to large equipment, such as R-2600's and R-4360's. No engine damage, no propeller damage, nothing.

[currawong]

SNS3Guppy,

Are you saying "I have not seen it therefore it does not exist"?

Just asking:ok:

[Chimbu chuckles]

If a 180 turn on the ground can do that damage what are the 'reversal turns' you do 100s of times a day doing?

How come Bob Hoover's engines routinely exceed TBO with the hammering he gives them?

More likely to be poorly overhaulled or poor QA at the engine factory IMO.

The number of 2 - 4, and some less, minute sectors in 185s we did in PNG were virtually all preceeded with exactly that type of start to the takeoff roll...and there were 10000s of them...and our engines always made TBO.

What sort of gyroscopic loads does bounding down a goat track place on the crank, seals, journals etc...more than a 180 turn..even one conducted briskly.

Even Chief Engineers are human and just as prone to belief in ideas that are purely based in speculation or the biasses of their teachers.

[currawong]

But are you big enough to answer my question Chimbu?

:ok:

[airag3]

A bit off topic from flap extension during take-off roll but the new one of gyroscopic loading on props during turns is a worthy replacement.

Fundamentally I reckon it's about prop rpm and rate of change of direction , and the times these are at their highest ( for me at least) are during pull-out over trees or similar tall object at the end of a run and like-wise the rapid pitch up when arresting descent over same at the beginning of a run, so the change of direction is in the pitching plane not laterally .

While I wouldn't recomend high power sharp turns whilst taxiing I think there might be a bit of over reaction involved as well.

BTW chimbu , P-turns at the end of a run went out with the advent of GPS guidance as we "Race-Track" most jobs now, but even when we use a P-turn the rate of turn in a heavily loaded Ag'aircraft is low ( when I fly it anyway).

[3 way valve]

Good thread you've started here LLD, even if we are getting off the topic a bit.... When I first started ag flying in an ag wagon, an old pilot told me to pull on the flap half way down the runway when the tail started to feel light to help get it in the air. That was the method he'd always used. I think I tried it a few times, but it was hard work on the flap motor (read left arm) at a time when your hand should be on the throttle or dump lever (depending on the stage of takeoff). But since I've been flying turbines, I set the flap before takeoff, one less thing to worry about . The best invention ever was putting it on the stick (in AT's), no fumbling looking for switches in the heat of the moment.

Just wondering RDA, what did you mean about the downwind turn being all in your head??

Anyway, off to spray some army worm, yes thats right the army worm have marched in god bless em...:O

3 way valve

[Rarely Dble Amber]

Just wondering RDA, what did you mean about the downwind turn being all in your head??

Just the "apparent" performance loss when turning downwind

A level turn in, say, a 20 knot wind.. the aircraft performs the same going downwind as it does into wind... but in a full Pawnee on a hot gusty day it sure feels better when going into wind. This is of course not the same as pulling up and turning into a strong wind gradient, which is basically flying yourself into wind shear situation. :oh:

Dropping flap at 65 knots feels good, because you suddenly have all this lift... however, had you had that flap there from the get go you would have had the exact same amount of lift.

[3 way valve]

the aircraft performs the same going downwind as it does into wind...

I understand the theory you are talking about RDA, the whole "flying in a moving mass of air" theory. However this theory is slightly flawed when applied to heavily loaded aircraft. Say for instance you are taking off with a 10kt x-wind from the right with an obstacle straight ahead (say trees) but clear ground left and right, which way do you turn immediately after takeoff??? I will go into wind everytime, in this case right, especially with a full can. The moving mass of air theory doesn't take into account inertia. I am not very good at explaining this but here goes..

You are flying across the wind and turn downwind, the aircraft does not immediately accelerate with the wind due to the inertia. There will be an initial reduction in performance until the aircrafts inertia is overcome and then the aircrafts performance will return to the previous level. The performance reduction is only momentary, however flying a fully loaded ag plane, it can be that moment where you get that sinking feeling.
When the aircraft is light, the performance drop is so minimal it doesn't register, however when it is fully loaded the problem is exacerbated.
Like I said, I am not very good at explaining it I'm just an ag pilot,someone else might be able to do a better job than me. I am sure some people may disagree or like to shoot holes in my theory, but i'd love to hear some discussion on it.

3 way valve

PS Sorry LLD this is way off the thread you started!

[Rarely Dble Amber]

Yep, way off topic, and much more fun to discuss over some cold beers.. however, still good stuff...

I believed the exact same thing years and years ago 3 way, It took an old instructor of mine many hours (and several beers) to convince me that there is not an actual performance loss in the downwind portion of a level turn, regardless of how heavy you are. Climbing turns such as after take off and during a reversal turn are different.. If it is blowing 15 to 20 knots on the ground, then 50' up it will be 20 to 25, so you are climbing and turning into a 5 to 10 knot windshear (or windgradient, what ever u want to call it), not only that, but if you are climbing to aviod obstacles then climbing into wind will increase your angle of climb (and rate of climb, given the windgradient).

Think of an airliner at 36000 feet in a 180 knot jet stream crosswind, do you really beleive he would lose 180 knots of airspeed if he did a steep turn downwind? (Might have to poke into a jet jockey forum and ask that question :D)

When climbing into wind, sure, definate and actuall performance advantage. When doing a level turn, typical on topdressing, seeding and baiting operations, turning downwind will not cause you to drop out of the sky... but it sure feels like it sometimes .. and thats my point:ok:

[currawong]

level turn downwind = good (plane does not know the difference)

climbing turn downwind = bad (gradient becomes critical)

turning after take off probably a climbing turn...

level turn, downwind, ignore outside visual cues = no loss in performance

upwind of obstacles still a good idea - it's where the updrafts are