Piper Arrow Speed Mods

Piper Arrow Speed Mods

Alright so I've researched the past forums, and it looks like there is a lot of info in the speed mods arena but I'm looking for a little more if I can.  Our flying club has a doggie 1977 naturally aspirated Arrow  ~125 true at 24 squared.  The plane is completely stock, and I've taken on the challenge of researching speed mods.  I've called and researched Lo-Presti, Knots 2 U, and Laminar Flow systems.  Per the research I've done we're going to start with the rigging, but after that I'm looking for anyone with actual experience with an Arrow and see if anyone has any real results or recommendations?  I'm not looking for the wild claims of 20-25 knots, but would like to see 8-10 knots out of it realistically in the under $5,000 range.  Any actual experience or recommendations with some sort of measured results would be great!

Edited By: ihawk16
2012-03-16 18:00:39

ihawk16
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Re: Piper Arrow Speed Mods

I've owned an Arrow II since around 1997.
The first thing we did was to install the Laminar Flow Systems mods.
The mods which go on the bottom of the wing are pretty standard practice, consisting of aluminum gap seals (flap AND aileron) aluminum hinge fairings (front and back), and aluminum wheel well fairings. Together, these will give about 7 knots (8 mph) The gap seals also give a more positive rate of climb. and are very noticeable when you rotate at takeoff.

Where things become interesting is when you add the fuel tank fairings and do the wing smoothing. The fuel tank fairings cover the many many rivets and screws on each side of each fuel tank. They usually give about 4 mph on their own, by reducing the parasite drag... there are lots of rivets!

But the real icing on the cake comes when you also smooth the surface of the wing, on the upper leading edge. the idea is to prevent the laminar flow from separating and becoming turbulent until it reaches the point where the chord is greatest, at the main spar. If you do this successfully, the extra gains are dramatic.

On my Arrow, the new cruise speed is around 153 knots, up from around 136, and many owners have achieved similar results. But there are a couple of caveats... the engine and prop must be smooth with as little vibration as possible. If the engine starts to run a little rough, there can be a drop of 6 knots or so.

There is also a remarkable reduction in stall speed with the Laminar Flow mod. On a Dakota, I measured about a 7 knot drop in stall speed, and the owner panicked when he found me flying so slow on final. He had to get a flight instructor to teach him how to land again!

I think that the wing smoothing would be an ideal flying club project.

Good luck

Robin
www.laminarflowsystems.com

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Re: Piper Arrow Speed Mods

Robin,

Do you have any pictures of your plane, most importantly the wing smoothing that you would be willing to share.  Did you have to repaint the wing when you did it?  Does it add any weight?

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Re: Piper Arrow Speed Mods

I'm sorry to have taken so long to get back to you!

To find pictures of a smooth wing, you should go to www.laminarflowsystems.com , in the left margin, click on GALLERY, and in the second row you'll find a couple of pictures of a smoothed wing. It's a actually a Cherokee 140, not an Arrow, but the result is the same.

To understand the process, you can see me doing it on you tube. Look for "laminar flow systems wing smoothing" and you'll see how it works. A good body man can do the whole wing in two days, and the results will be great. Then you need to repaint the top of the leading edge of the wings.  That's what we did for the plane in the pictures. Only the front upper part of the wing was painted. The Cherokee 140 cruises at well over 150 mph, and the Arrow does  over 150 knots.

Wing smoothing also has great effects in stall speed and in rate of climb. This is not magic or sleight of hand. The airfoil section used in all Cherokee derived planes requires the upper leading edge of the wing to be smooth to perform as designed. Piper apparently did not read the fine print of the specifications... unlike Mooney and the Grumman Tigers, which have a very smooth wing, and perform accordingly.

I hope this helps.

Robin

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Re: Piper Arrow Speed Mods

RobinT-

Thanks for the response.  Anyone else out there with any experience with mods they might be able to share?  I'm going up tomorrow to do a timed climb to 7500 msl, and run a gps course at 7500 and 3500 to get measured results on the true airspeed.  The plan is to run this test after each mod and post the results.

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Re: Piper Arrow Speed Mods

Ran the airspeed test for a baseline.  Results at 24 square at 3500, and WOT (22.5 manifold) with 2400 at 7500  This is a completely stock P28R-201 Arrow III with a 2 bladed prop:

7500' 134 kts true
3500' 124 kts true

Time to climb from 950' runway and wheels up to 7500' msl at 25 squared was 9:18 minutes.

Once the mod list is decided on, and installed, I'll post the results as well. 

Again anyone else out there with real experience with mods?

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Re: Piper Arrow Speed Mods

Here are two things to consider when doing airspeed measurements.

First, if you really want to do accurate apples-to-apples before-and-after comparisons, be sure to do the runs at the same density altitude - pressure altitude adjusted for temperature (and humidity, if you really want to be precise).

Second, if you want a precise and accurate measurement of your true airspeed, use GPS and the method and calculator here:
http://www.csgnetwork.com/tasgpscalc.html

The analog airspeed indicators in our Cherokees are imprecise and often a bit inaccurate.

-Jim

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Re: Piper Arrow Speed Mods

josulliv,

Thanks for the tips.  We did use that method, and calculation for the airspeed noting OAT at each altitude, and current field pressure.  Just so we had a measure.  The listed speeds came from that calulation, and the 430 ground speed indications.  Didn't really even note the indicated analog speeds.  It'll be tough to line everything up the same, but we'll do our best.  If you're curious the OAT was 22F and 25F respectively.

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Re: Piper Arrow Speed Mods

ihawk16

Drooping Gear
Robin's company makes some great products, and has some great experience.
As well as the rigging - also check the undercarriage of the Arrow. My friend's Arrow required a small amount of adjustment to get the main gears to properly seat in the stowed position, and not droop slightly. This slight drooping of the main gear can add a bit of drag, slowing the plane.

Wax
Also consider a good clean of the plane. The bottom of the plane can accumulate some oil, then attract the accumulation of dirt to this oil, generating parasitic drag. The CAFE guys did a comparison of a non-waxed and waxed Mooney a few years ago and saw a 5 know speed difference. The report can be found:

http://cafefoundation.org/v2/pdf_cafe_r … 20PICT.pdf

My slow Cherokee Six was sped up by Robin's Speed Pants - maybe one day I will be able to keep up with a slick Arrow!!

Andy

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Re: Piper Arrow Speed Mods

Bigandy-
We've got a cherokee six 260 as well.  Starting with the Arrow as the test bed for the mods, but I've heard some decent reports on the speed pants for the six.  I'm a little wary of the 10mph claim over the stock pants, but it would be great if they really do that.  What did you see if you don't mind sharing.

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Re: Piper Arrow Speed Mods

I'm new to the board, and interested in whether you've made any progress on this project?

I also fly an Arrow II. I have a 3-blade but otherwise it's similar. Have you removed the gear-retraction mast? My aircraft has the automatic retraction deactivation kit installed, so the mast is useless drag. I don't know if it's legal to remove that.

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Re: Piper Arrow Speed Mods

Welcome to the forum!

I would not worry about the automatic retraction mast... even if it were as bad as it could be, it would not cost as much as 0.33 mph in speed. Consider that the flap hinges, all six of them are less than 3 mph... and compare the shapes. The flap hinges have a drag number of around 1.2 (in relation to frontal area) and the automatic reduction mast is in the region of 0.3.

If you would like to find out more, and discuss, the things you can do for your Arrow... please call me Robin, at 386 451 1957 or just email me at This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Best

Robin
Laminarflowsystems.com

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