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Speed Mods

Anyone installed any speed mods to their aeroplane? We have just bought a couple of STC kits for our Commander to try and add a few knots to the top end. The ones we bought are:

  • Aileron and flap gap seals. I reckon this should give us 2-3 kts I hope?
  • An Aerodyme Superstream kit which is an STC to change the incidence of the tail plane. This in turn reduces drag and according to the STC owner this reduced drag can be equated to an increase in 20 effective HP on the engine at cruise speed (+ 8 Kts) or a reduced fuel flow of 2 USG per hour.
  • Changed the beacon fairing to recess the beacon into a fairing rather than having a great lump stuck on top of the rudder. 1 Kt maybe?
  • We are also installing a votex generator STC. Although this won’t help with top end, this should make slow speed handling better and also increased ROC and short field performance better. It is quoted at giving at least 150 fpr ROC increase.

Hope it all works! I guess the Ultimate Commander is the IO590 powered 330HP TC’d Superstream Super Commander…..One day maybe :)

EGHS

I hope you know that the effect of several speed mods is not cumulative?

However, I would be interested to hear about the results in your case.

BTW, I have never heard about an IO-590. Neither does google…

Last Edited by boscomantico at 17 May 13:55
Mainz (EDFZ) & Egelsbach (EDFE), Germany

The Lycoming IO-580 built for the Extra 330. The Cessna NGP was supposed to rely on it.

Aileron and flap gap seals. I reckon this should give us 2-3 kts I hope?

The negative effect of those is most likely a longer landing distance and more difficult landing technique.

I don’t believe the IO-580 is the solution.
Get a hot shot mod and add a turbo. I’ve done it and it makes more sense than adding a knot here and there.
My mission profile is about 3 to 4 hr legs and it had changed the game completely.

United Kingdom

Rumour (never substantiated) on the Socata owners’ group was that gap seals worked on the TB9/10 but not on the TB20/21. I know no more.

You could install 9.5:1 pistons. They are the highest CR that still works with 91UL without detonation (I am reliably informed by a US Exp engine builder) You get an SFC improvement proportional to approx the square root of the CR increase so e.g. a 10% increase in the CR gives you 5% more HP – for the same fuel flow.

The big VHF antennae rob about 0.5-1kt each. Recessing the various antennae will make an extra few kt.

Last Edited by Peter at 17 May 15:55
Administrator
Shoreham EGKA, United Kingdom

Sorry IO580 not 90.

I think they also did a hot shot TN version of this Commander too, which I imagine would be quite impressive.

EGHS

2 different STC the IO580 and the hot shot. You cannot mix the two.

United Kingdom

Here is how you can get over 3kt

Administrator
Shoreham EGKA, United Kingdom

Am not sure that you ASI is sensitive enough to measure the increase in airspeed. I fitted X2 STC but also O/H the engine, got 5KTS extra.

Some years ago I owned a Piper Arrow III with a full Knots2U speed kit – flap and aileron seals, wing root seals, wheel fairings to the wing undersides, and I reckon that the total gain in speed was about 3-4 kts, and this was with a 3 blade prop and a fresh engine. It did climb very slightly better than standard, and it did stall about 3 kts slower than book. However, it did take some practice to land it smoothly, as the transition in the flare from flying to ceasing to fly was quite abrupt, and i flew with a succession of high hour pilots (who had many hours between them in retractable PA28’s and PA32’s) who all put in ‘aircraft carrier’ landings. All in all, the improvement was slight, and hardly worth the embuggerance.

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