Top Models Pilatus Porter 3.2M Mod's and Pic's

[Marnochs]

Interesting occurrence yesterday at the Salem field "Turkey Tow". We started towing at 10:01 am and never stopped untill about 4:30pm or so. The Porter went through 4 gallons of fuel and almost all of its 9000 Mah!!!!
The last tow, Don was flying the Tug and said the flaps wouldn't deploy, he landed the plane and then they worked. When I pulled up on them, I could pretty easily make them move. Since i have JR8711's in them, there is NO way they should move. Upon arriving home, I charged the two 4500 Mah battery packs, which are 6 v packs, and one took 4358 and the other 4633. The ignition pack took 2360 ( it was a 4 cell 4500 )

I must say I am surprised. I would have never thought the plane would use up 9000 Mah. In retrospect, they are all digital servos, the flaps at full deflection, diving out of the sky, surely puts a strain on the servos, which means more juice, and it was running for 6+ hours.

We are luck there was not a major disaster. I pass this on so we can all learn from this. This time it had a good outcome, for once.

Other than that, the Porter was flawless. With the new three blade 27.5 X 12 prop, the plane became silent at about 1500 ft. and the downline braking with it spinning up front was incredible. Putting that prop on the front reduced the noise 3 times over the wood prop.

We figure close to 100 tows yesterday. 4 different tow pilots and no issues.....Porter Power!!

LEN

Hi Len
Looks like you almost had your own NTSB report for the Porter, good to hear its just a "note".
John Wilson burnt up a flap servo doing the same thing ( diving from altitude with the flaps extended ). It was rather exciting when only one flap came down.

And of course there's always the full size operating parameters to consider (Vfe- max speed w/flaps extended)

You might consider sending the flap servos in to check out the motors - they were pulling high amperage during the short desents. After flying the Yeti for 4-5 hours, I normally have to put about 4000mAh back into the 8000mAh capacity batteries.

Scott

[Gunny]

I normally have to put about 4000mAh back into the 8000mAh capacity batteries.

Taking out or using 50% of the battery capacity is a good saftey margin. That's when all things go as planed. But, when there are high loads "or even binding" exerted on control surfaces (especially digital servos) the amerage use goes way up and consumes more mAh out of the pack(s). The volt magic is a programable precise piece of electronic equipment. It is accurate to .001 (thousands of a volt) and you program it for your parameters. ie. digital or analog servos used, maybe half digital and half analog etc. You program the unit for the type of battery pack being used and its' mAh capacity. ie. NiMH, NiCD, Lipo's and even A123 LiFE. Finally you program the satey margin (when you want the yellow caution and red "dont fly" lights to come on). You have a few choices here. Conservative (top xx% of the capacity, moderate (50% capacity) and finally aggresive (bottom xx% of the capacity). The unit has a very good feature in it also. It will dispay peak low voltage for that last flight. ie. doing a full throttle snap roll.

Although I use a 1/4 scale tug. I carry enough fuel on-board for 30 minutes of aerotowing. (I use the Tx total timer to gauge my fuel level, similar way of how Jim D does it). I use dual switches and a single 2300 mAh A123 rx pack with a voltmagic on-board programed at 50% moderate capacity. So when the next guy fumbles around to get his glider all hooked up, I look down through the window and observe the meter. When it comes time to refuel the tug I just throw the rx on charge and since it's A123 it's done in less than 10 minutes.

It would have been a shame to see that Porter create a divot somewhere in the corn field.

Don't check your brain at the door! Know what's going on with your equipment! Check your packs before each and every flight.

Just sharing My .02 cents.

Gunny

[Wilgaman]

Len and Marnochs:

You both have some very good insights. Thanks for sharing!

The flaps should be used for areas of flight where more lift is needed in slower-speed situations, such as landing and taking off. Diving back to the field from a tow at high altitude should not be carried out with flaps deployed. Fast speed flying on flaps deployed drains battery incredibly fast, as servos (and especially JR8711's) require an immense amount of amps, because they are struggling to keep the surface from moving. The same situation/concept applies for landing gear in sailplanes. If not correctly set up, the landing gear servo will keep working and use up those precious mAh's very quickly. I would not recommend using Nickel-Metal Hydride batteries in PowerSafe recievers. Using Lipos of very high capacity is what I would recommend, especially for towplanes.

Mark

[Len]

Thanks for all the input guys.
Mark, I could not disagree with you more. The reason to use flaps is to increase the angle of decent without increasing speed, in the case of a tow plane or a parachute jump plane. Obviously, there are limitations on speed. In my full scale aircraft. 1 notch will increase lift, 2 notches a little more and 3 notches is just drag.

The issue here is not the use of flaps, it's the lack of attention to flight time and battery usage.
My plan is to reconfigure the flap linkage so full flap deployment will be over center, therefor elimination any servo strain.

Again, thanks for all the input, even if we all don't agree, its nice to hear the other side of the argument. ( so to speak )

Len

[Wilgaman]

Mark, I could not disagree with you more.

Len,

The point of my post was to stress that you do not place the flaps in the full down position immediately after releasing a glider from tow. The correct procedure after the release is to immediately dive away from the glider and head directly for the runway. Placing the flaps to full would exceed Vfe speed. The airplane should remain in the clean configuration until preparing for landing.

Mark

[Wilgaman]

Steve P, sorry I had to borrow your picture.

Thanks,
Mark

[aerowiz]

Flaps are for weak pilots, I prefer to side slip inverted, with a 1/2 negative snap on finals.

Got to have some flair being a 3d Junkie. of course that fancy flying is with a 40% yak and not a porter.



I dont do flaps because of the load/current drain on my servos/flightpacks.

I also have done a bucket load of towing with the 3.2 pilatus porter-3w 110 and found the quickest way up and down with up to

1/3 scale gliders is to use no flap at any time during flight.

[Len]

2 against 1, thats no fair......!!!

[aerowiz]

Hey Len, No sides here just i have a lot of experience with one of these tugs (as im sure a lot of other people do)

One trap that people fall into is realising what flaps do for full size aircraft. Which doesnt really help models. Flaps are a lift generater, they also

give the aircraft a nose down attitude while maintaining a straight flight path, this enables the pilot more of a view of the runway for landing.

With a model, I dont actually need a tug to have a nose down attitude because I am standing outside the aircraft.

The next point is working out where the cofg should be for tugging. Ive found in most aircraft that the cofg really affects how a plane lands.

The optimum for straight and level flight stability is generally too nose forward for sweet landings, however, move it back a touch and the aircraft

Is a real pussy cat to land. For example, Nigels 3w110 porter has a 200gram block lead under the tail plane and now its a nice landing aircraft.

So i figure that a tug with its high frequency of takeoff/landing cycles should be in the easiest cofg state to get on the ground.

Please, if anyone is putting one of these planes together dont go and make it tail heavy on the first flight, fly it and move it back a little at a time,

Generally manufacturers state too far forward cofg to add some safety margin for setup error.

[Wilgaman]

Hey Len,

I didn't want to sound adversarial, I just wanted to get my point across from my prior experience's. We have a great website with wonderful people and I enjoy learning from everyone as well as occasionally adding my 2 cents. We are all well aware how expensive mistakes can be and hopefully we can help each other with our own past experiences to prevent future issues.

Mark