Menu Sign In Contact FAQ
Banner
Welcome to our forums

Making a PA28 10 knots faster (and PA28 v. C172)

I’ve always thought the PA28 could do with cruising 10 knots faster.

Now the props in good condition and has a fair few years and hours to go. I also don’t want to raise the fuel burn.

Any ideas what mods would be the best?

I own a Warrior which I lease out. The previous owner did a nice job and invested in wing root fairings, upgraded wheel spats, flap and aileron gap seals, and Horton wing tips.

At 2,000 feet ISA it cruises at 120KTAS at 75%, so in theory full throttle 75% (6,000 feet ISA?) should produce 125-130KTAS. I would like to test this but haven’t got round to it as the aircraft gets reasonable useage.

The Horton wing tips probably do a nicer job reducing wing tip vortex drag than reducing the stall speed, although in theory the stall speed is supposed to be about 5 knots lower. As my main conveyance is the Super Cub I find it hard to process in my head the Warrior as a STOL.

The last Warrior with improved wheel spats, engine cowling is supposed to deliver 126KTAS, only 11 knots less than a constant speed, retractable Arrow iii.

Enstone (EGTN), Oxford (EGTK)

The club I’m a member of bought a 2004 P28A Archer III which came fitted with flap and aileron gap seals, wing root fairings but honestly, there is little difference in speed between it and it’s older cousin – a 1999 Archer III. We had expected it to perform better but it doesn’t, both cruise around 115 – 120 TAS at 3000 feet. The climb performance though is better……

Here’s a picture of the modified aircraft, you can see the gap seals and wing root fairings clearly…

Last Edited by Steve6443 at 15 May 19:43

Probably to sell it and buy an M20 would be worth a couple of knots…

mh
Inside the sky.
EDXE, EDXF, Germany

mh wrote:

Probably to sell it and buy an M20 would be worth a couple of knots…

Around 30kts

EGPD / OMDW / YPJT, United Kingdom

I think when modifying a fixed prop pitch airplane to go faster the propeller pitch should be modified too. It is not much use to make the air frame more slippery if the prop bites the same amount of air than before the mods. Using “cruise propeller” will affect takeoff performance for sure but since there is no possibility to change the prop pitch in flight some compromises must be made.

I have found very little info about modifying propeller pitch or switching propellers. If anybody knows how to calculate prop pitch, altitude and power relations I’d be very interested. Or if there is anybody who has been changing/modifying fixed pitch props it would be nice to hear your experiences.

Last Edited by AirV at 16 May 21:59
EFHF

@AirV, MT-propeller offers electrically adjustable 3-blade props for PA28-180/181/235/236 (as well as many other aircraft types). The cost is about €9000 + installation, and besides higher speed and/or lower fuel consumption you also get a somewhat higher prop ground clearance due to shorter blades, as well as individually repairable blades with stainless steel- or nickel-clad leading edge.

Last Edited by Ultranomad at 16 May 22:28
LKBU near Prague, Czech Republic

Ultranomad wrote:

@AirV, MT-propeller offers electrically adjustable 3-blade props for PA28-180/181/235/236 (as well as many other aircraft types). The cost is about €9000 + installation, and besides higher speed and/or lower fuel consumption you also get a somewhat higher prop ground clearance due to shorter blades, as well as individually repairable blades with stainless steel- or nickel-clad leading edge

I own one and fly with it weekly. It’s good for about 5 kts in cruise and also increases climb rate. It has a constant speed mode as well as being manually adjustable, with the operating mode selected by a switch. The blades move about 1/6 as fast as a hydraulic prop, but that is not a huge limitation for cross country type flying.

FYI construction is uniformly amateurish – plastic tie wraps and no conduit to secure motor power wiring to rotating propeller hub, same wiring connected with exposed to elements, uninsulated screw/lug type connectors, tiny little commercial quality motor rotating with prop, flexible stamped steel brush block & speed sensor bracket that has to be tweaked or shimmed to properly align brushes to slip ring etc. I also had a lot of trouble with the speed sensor, resulting in CS mode prop control being highly unreliable but they’ve improved the sensor design and since replacing mine, my prop control has been fine. If you do come across one with a sensor having red silicone style insulation around the wiring, FYI MT advised me to replace it immediately as soon as they understood I was still running it (at my cost).

My input would be that if you really do need a constant speed prop for a solid crank engine and are prepared to fuss with something that is built to a price it does work, but it’s not really aircraft quality. I casually mentioned that point of view to a workshop owner I met in Germany and his response was to say (in typically restrained German style ) “I’ve got a lot of worn out motors if you need some, they are junk”. Further conversation got him to say “OK, this prop works for a privately owned plane like yours flown 50 hrs a year but they are junk for anybody else” which I took more or less as agreement with my own experience

Last Edited by Silvaire at 17 May 04:26

Speed mods are a huge business as people naturally want to fly faster. What most of them do is to make the plane look nicer but rarely do you get real significant increases in speed. Calculating the huge investments, I can imagine upgrading the plane to something a bit faster will make more sense.

For a PA 28 the logical upgrade would be an Arrow or a Grumman AA5 Tiger. The Arrow has essentially the same cell with 20hp more and a retractable gear and variable Prop. The AA5B has the same engine and fixed Prop but is significantly faster,up to 140kts TAS.

Also a vintage M20 will get you about 140 to 150 kts with the same engine (C model) or the 200hp injected engine in the F or E.

(of course guess what the main discussion is with vintage Mooney owners. Yes that’s right : Speed mods. 201 windscreen and cowling yield 10kts, but are expensive. So why not upgrade to a 201?)

Last Edited by Mooney_Driver at 17 May 07:15
LSZH, Switzerland

A Jetprop will go even faster, but 10kt more on a PA28 which already has the right wheel cowlings, not likely.

The best speed mod, especially on a short range plane, is bigger tanks :)

Administrator
Shoreham EGKA, United Kingdom
43 Posts
Sign in to add your message

Back to Top