Pilot Skill: Intermediate
Manufacturer: E-flite
Power: O.S. .25 2-stroke glow engine
Wingspan: 62 in.
Kit Includes: Covered kit, wheels & landing gear, hardware

Editors Note: This article only covers modifications and flight characteristics of the E-flight Piper Pawnee 15e when converted to glow power.

Overview

The Pawnee is a very unique aircraft for the radio control world. While most fliers opt for warbirds or the more popular civilian aircraft, E-flight went another direction by introducing a classic American crop duster. We were pleased to see E-flight manufacturing such smaller scale aircraft for those of us who don’t have the cash to blow on a 1/4 scale radio control. Bonus points here.

As usual E-flite’s kits are built solid, covered great, and come with pretty easy to follow instructions for a first time ARF builder. There really isn’t much that surprised us when we opened the box – all the parts were in the right place and nothing was broken. What did raise eyebrows was how light yet very sturdy the airframe seemed to be. This was good as we had full intentions of installing a loud vibrating engine as its power plant.

Features

E-flite’s Piper Pawnee 15e is obviously made for electric flight. However, we didn’t have the funds to purchase the required electric power plant so we decided to use an OS .25 glow engine that we had lying around. Ironically, it’s a great choice as an alternative power plant. We give you a brief overview of the engine installation in Additional Notes since this modification isn’t part of the original kit.

Most of the kits assembly was straight forward. Install an aileron servo here, glue a horizontal stab there, screw the landing gear to the fuselage, epoxy some wing halves, and Voila! While we were expecting more work then normal with the engine, what we didn’t expect were the issues we ran into with normal kit assembly. Below are the two glaring negatives about this kit:

The Tension Rises

The E-flight Pawnee kit fails (yes, we said fails) when it comes to installing the servos and pushrods for the horizontal and vertical stabilizers (rudder & elevator). Our question was, “Did anyone at Horizon Hobby actually build this thing?”. When we installed, per the instructions, the pushrods and then tried to connect them to the recommended mini servos, the tensions on the pushrods to push and pull the control surfaces was so great our servos freaked out!

The recommended servos couldn’t handle it. E-flight: You need to come up with a better way to connect the horizontal and vertical surfaces of the Pawnee. Your Y-connection (see images) to work the elevator has so much tension we had to install a standard full size servo in order to accomplish the job.

Lucky for us our rudder servo was indeed strong enough that with a little bit of bending and tweaking to the pushrod we were able to get it to perform smoothly. Make note of this: You’ll need patience and a servo with some Gusto! to run your elevator as well as a strong mini servo for your rudder. (See our recommendations in the specification above.) Unfortunately until E-flight fixes this issue purchasing stronger servos was the easiest way around the snafu.Though the mini metal gear servos cost more, they’re an investment and will last you a very long time in many aircraft (we have several).

Tired of Problems

We’re not sure if the manufacturing process is off, but when we installed the tires for the landing gear, they rubbed so much on the gear mount that we had to shave off a portion of the tires inside edge in order to get any spin. It wasn’t a huge deal but after the above problem we wanted a break. Perhaps we just got bogus gear – but be aware that you might have to shave off some foam to get the tires to work properly.

Flight Performance

First off, we recommend this as a second aircraft to anyone. It is a great low wing starter and with such a dramatic dihedral in the wing it is very stable in even windy conditions. On take-off our modified Pawnee took about 55 feet to get airborne, which we figured this was due to the added weight of the OS .25 and fuel but regardless, we liked the effect as it added immensely to the scale realism.

But one thing to note: If you’re not familiar with a low wing glow powered aircraft, the Piper Pawnee 15e comes across as very ’squirrly’ on take off. We almost tanked our Piper with the first take-off – Just be careful. Yet, when in flight the Pawnee is extremely stable. So much so that when we tried to do a loop high in the air, it ended with us flopping around like a fish out of water.

F-15E Night Strike Pilot

Add scale realism to any airplane with a Dragon Action Figure.

We realized then that the Pawnee is not made for aerobatics. That being said, we handed the controls off to our resident newbie and she took to it like a pro. At first there was hesitation since we had 12mph winds, but after some coaxing she took over. Personally we wanted to see if she could handle it in winds. It was the ultimate test, Newbie vs. Wind. Who will win? Well, she did. The Pawnee performed great for her and she was all smiles while watching her scale bird fly overhead. We offered up the opportunity to land but she declined saying, “It looks too good and I don’t want to ruin it.” We understood. After all it is her Pawnee (and her first glow powered model).

We had some strong cross winds and played it safe by flying out for a long landing approach. Surprisingly, the Pawnee didn’t give us much trouble and we even had to throttle back to idle in order for it to float down to the runway. We touched down with a few minor bumps and given a calm day we figured the Pawnee would land better then most trainers.

Summary

The Piper Pawnee 15e would be a good second airplane for someone with advancing skills. Especially for those seeking more scale appearance without the higher price tag. Our guess is that the performance would be almost identical with an electric power plant installed since pound-for-pound they’ll end up weighing the same in the end. The Pawnee can flip over quickly in flight if you push it, but keeping your control throws low will avoid this completely. The large dihedral really sets this airplane apart in performance, looks, and makes your landings professional too.

We recommend it as an ‘all weather’ flying machine since it handles winds better then most airplanes in comparable size. Now if we can only figure out how to install a bug sprayers for our air field we’d be set!

Recommended Parts & Accessories

Additional Notes

 

  • Modifying to glow
    We installed a OS .25 glow engine into our Pawnee knowing it was going to be more cost effective to run an engine and burn fuel vs. buying LiPo batteries and all the electronic. But we were lucky in having an extra engine lying around (and we were curious if we could do it). We didn’t know what to expect other then a lot of extra work and were really surprised when it took us less time to modify the kit for a glow engine then it did fixing the pushrod issue! Below are a few bullets on what we did as well as some pics if you decide to do the same on your Piper Pawnee 15e.
  • Engine Mount
    We bought a Great Planes Adjustable Engine Mount (for .20-.48 sized engines) and found that it lined up PERFECTLY to the threaded holes for the motor that E-flight recommends. We were shocked and very pleased. You’ll need four (4) 1.25″ hex screws w/bolts to secure the engine mount to the fuselage. It’s really that simple. We mounted our engine at a 90 degree angle* to keep all the ugly stuff on one side of the fuselage (*Note to the newbie: Most engines you can mount in several different orientations on an airplane.)
  • Beef Up The Structure
    We wanted to make sure the fuselage could take the vibrations of our engine so we epoxy 1/4″ hard wood to the structure. Additionally we sealed the entire region of the engine with thinned out epoxy. Mix 2 oz. of 30 minute epoxy into a plastic throw-away cup and add 10-15 drops of rubbing alcohol. Mix it up in the cup with your brush and start painting. The epoxy will seal the wood from the engines oil and fuel while also helping to strengthen the structure.
  • Engine Cowl
    Get ready to so some grinding. Though most of the engine fits very nicely under the cowl, you’ll need a Dremel to grind out areas for the muffler, engine head, and needle valve. We start by drilling pilot holes and then switching to a sanding bit and taking it slow. Don’t rush! It’s better to be slow at grinding away and get the perfect fit, then to rush it and end up with a cowl that has holes all over it.
  • Exhaust Deflection
    Since the muffler of the engine doesn’t quite clear the aircraft’s fuselage we decided to install an exhaust deflector. Unfortunately it kills a small portion of the scale looks, but we’d rather not be an oily mess after each flight. It’s a sacrifice we decided to make.

14 Comments

  1. Aleksandar
    October 22, 2008

    Great site…keep moving

  2. Konstantinos
    August 11, 2009

    OMG…

    The information you provided is so helpful and tempting to buy a 15e Pawnee now…

    Hehe…

    It could be awsome to also upload a video of it flying.
    What prop did you used with the 25LA?

    Konstantinos
    Athens/Greece

  3. Konstantinos
    August 11, 2009

    Ups,
    i found the prop…

    What about the servos?

  4. Chatter
    August 12, 2009

    Konstantinos – I recommend Hitec HS-82MG Micro’s for the throttle and the rudder. While expensive they are small and powerful. Plus, they’ll last you a long time. For the elevator you’ll need a standard servo w/lots of torque, like the Futaba S3003 Servo which is a standard servo that has the power to push/pull that thing! Using the standard servo makes for a snug fit in the fuse but will do the job nicely. 😉

    Hopefully E-flight fixes the issue with the elevator, or perhaps we had a bogus kit – but in my experience there was no way a micro/mini servo was going to move that thing. it was just too tight!

  5. wjr334
    September 1, 2010

    do you have a parts # on the engine mount I have two pawnee 15e i would love to do a glow engine

  6. Chatter
    September 2, 2010

    wjr334
    The mount I used was the following:
    Great Planes Adjustable Engine Mount .20-.48

    You can find it on Tower Hobbies website. Cheers!

  7. Leon
    December 18, 2011

    I am also assembling a Pawnee 15E right now (got it more than a year ago but only started on it now) and I was wondering where you bought the good looking pilot figure?. I in South Africa and will obvioulsy have to order from the US< I suppose.

    I have found that the 2 mm wire pushrods are exremely stiff in the piping leading to the tail. I am considering using 1.5 mm rods instead…or perhaps carbon fibre rods.

    Will go with a Turnigy C3242 1250 motor but I also have a .25 Webra Black top as a glow option.

  8. Chatter
    December 18, 2011

    @Leon –

    Pilot Figures
    The Dragon Action figures can be hard to come, can be expensive, by but they are amazing quality. I purchased 3 of them for $30+ each but have been using them in many aircraft thereafter:

    http://www.dragon-models.com/catalog/figure_pics/

    I found the figures at my local hobby shop before they stopped carrying them. Dragon doesn’t make many pilot figures but if you take some of their military figures and remove the guns, insignias, etc. you get a great civilian pilot look.

    Push Rods
    I agree about the push rods. I found the same issues and because of it decided to switch to a stronger servo to make it work. Your idea of going down in push rod sizing is smart. I didn’t think of that (clearly…) 😀

  9. Leon
    December 20, 2011

    Thanks for the reply, I will be on the lookout for these type of figures (or the like) on Ebay and in the shops here in South Africa.
    $30 is a bit heavy in terms of SA Rand at this stage though.

    With the festive season on us, there are plenty “action hero” type figures around in the shops. Now to find one that will fit, that is a total different story.

    Thanks for sharing your Pawnee experience with us, I for one appreciate it a lot.

    Have a great Christmas and a fantastic 2012.

  10. Gary
    August 2, 2013

    looks like a great conversion. I have that plane laying around, was currious as to putting in a 4 stroke. I have a OS 26 looking for a plane and an OS 48 laying around. do you think the little 26 4 stroke would be enough to fly the plane?

  11. Chatter
    August 2, 2013

    @Gary
    Given that I fly my Pawnee 3/4 throttle with the O.S. .25 2-stroke, the power of a .26 4-stroke should be ample. The benefits of the 4-stroke would be torque; which equals pulling power. Huge bonus! So I think you’d be 1-up on me using a 4-stroke of the same size. Plus, adding that beautiful sound to the mix would make for an awesome aircraft. All that said, keep in mind that my conversion was also more “scale” like in its power – there isn’t enough power to do turn and burn maneuvers with my set up.

    Doing as close of current day comparison as I can (since I can’t find data on the .26 4-stroke you have) you’re running fairly close on power (below). You’ll loose some speed with a 4-stroke but, you’re gaining power via torque and pull.

    OS 25LA
    Practical rpm: 2,500-16,000
    Output: 0.59 hp @ 15,000 rpm
    Weight: 6.9 oz (197 g)
    Recommended Props: 9×5, 9×6, 10×5

    FS-30S
    Practical rpm: 2,500-13,000
    Output: 0.49 hp @ 10,000 rpm
    Weight w/muffler: 10.4 oz (295 g)
    Recommended Props: 9×6, 9×7, 10×4, 10×6

    If you could fit that 4-stroke inverted into the E-flite LR-1A Pogo ARF 15e, THAT would be impressive!

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    March 19, 2014

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  13. john
    November 21, 2014

    I am building a Piper Pawnee from a plan, wingspan 68 inches. The plan does not specify the dihedral but the wing joiners shown on the plan indicate that this would be like 150mm (thats 6 inches) under each tip. I know the Pawnee has lots of dihedral but 150mm under each tip sounds excessive? Could anyone give me the dihedral and wingspan for a similar size model from which I could calculate the correct dihedral for my 68 inch wingspsn model. Mine will be a 40 I.C. size, Thanks, John

  14. Chatter
    November 21, 2014

    @John – you might want to check out the wiki on the prototype Texas A&M College Ag-1. They do mention, “It had a short centre section with no dihedral and outer panels with 5° of dihedral.” Granted this is talking about the Ag-1 prototype but, given that it is a 5 degree dihedral I’m pretty confident that your 150mm under each wing tip is correct. Even for the small 15e I have it sits around 3 inches off the ground at the wing tips. I’d do some research on the full scale and see if you can find any building specs. Hope this helps!

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