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TKS ice protection for a TB20

I have done the final sealant work on the TKS panels, going over one upper seal again (because it slumped by about 0.5mm), replaced the fuel totaliser (and checked it today against the airport pump – 0.7% error) so I have accurate fuel flow, and I am pleased to report:

  • there is no measurable speed loss (if there is, it is less than 1kt, but it may be going a bit faster!)
  • climb performance is not affected

Today I did a flight near Norwich, going up to FL195 in Class G and then being allowed to FL200 via Swanwick Military for a few mins, and it was still doing +100fpm at FL200 (-30C). Stall warner didn’t even come on.

This is in cruise, so again no performance loss at FL200. The +5 degree pitch angle is about what I would have expected to see.

The TKS fluid level readout is very affected by the pitch angle – it reads about 2 USG more (25% of the tank capacity) in a 5 degree descent.

Administrator
Shoreham EGKA, United Kingdom

Have you met icing conditions during the flight ?
Not loosing any of the ceiling is really a great news.
Claiming a speed increase is cheeky :-)

Congratulations Peter on the successful TKS installation – now you can fly with the eagle while I have to scratch with the chicken (non-TKS)

EDxx, Germany

Thank you It’s been a very big job…

No flight in icing conditions yet. I plan to give the system a good run when I next see IMC – so the stuff gets washed off. In fact the cleanest way to give the system a run is on the ground, because – apart from the vertical stabiliser – there is no runback and the liquid just drips off the bottom of the TKS panels so you can wipe it with a rag. On the VS it makes a mess but you can lay rags at the base of it.

I think this sealant bead makes a significant difference

BTW I don’t think a speed gain is impossible, because aerodynamics are just a tradeoff between performance, and meeting the 60kt mandatory max Vs for a SE plane.

Administrator
Shoreham EGKA, United Kingdom

I even think it improves the good looking of the aircraft, by underlying its leading edge.

I understand you can go faster if you make the wings shorter, but didn’t expect it by adding panels

Great job. Congratulations Peter!

LGMG Megara, Greece

Peter wrote:

Today I did a flight near Norwich, going up to FL195 in Class G and then being allowed to FL200 via Swanwick Military for a few mins, and it was still doing +100fpm at FL200 (-30C). Stall warner didn’t even come on.

Is that pic in level flight? So about 130 kts TAS up there?

Congratulations on a job exceptionally well done. I reckon a lot of the speed losses come from sloppy installation work.

LSZH(work) LSZF (GA base), Switzerland

Yes; level flight.

I have just realised the TAS subscale on the ASI is set to something totally dumb… but anyway you can work out the TAS. -30C is ISA-5.

The TAS at the operating ceiling is never very much, because by definition the IAS is close to Vs. Also the fuel flow is fairly high – about 10.5 GPH – due to having to run at best power and obviously this means max rpm. But this wasn’t the ceiling; it was showing +100fpm at FL200 and would have probably climbed to FL210 but I could not be bothered to ask for the extra clearance. They didn’t want me up there for long.

I am really surprised there is no obvious performance loss. I have heard stories of all kinds of numbers. The only owner who reported no loss is this TB21. He, Paul, was very kind to send me loads of photos of his installation taken while it was progressing and we used them for guidance. A picture is worth a 1000 words, as they say, and the 30 year old drawings contained various issues.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

The TAS at the operating ceiling is never very much, because by definition the IAS is close to Vs.

Isn’t the operating (service) ceiling the altitude where the max climb rate is 100 fpm? The airspeed at the absolute ceiling (where the max climb rate is 0 fpm) should be a fair bit higher than Vs as it is the altitude where Vx=Vy and Vx will increase with altitude.

Addendum: Grabbing the nearest POH (for a Cessna 172S), I find the Vy speed at absolute ceiling to be about 70 KIAS while the stall speed is 48 KIAS!

Last Edited by Airborne_Again at 28 Mar 08:08
ESKC (Uppsala/Sundbro), Sweden

Isn’t the operating (service) ceiling the altitude where the max climb rate is 100 fpm? The airspeed at the absolute ceiling (where the max climb rate is 0 fpm) should be a fair bit higher than Vs as it is the altitude where Vx=Vy and Vx will increase with altitude.

Maybe that is a matter of the definition. I vaguely recall the FAA applying +100fpm but the UK CAA applying +50fpm, which resulted in a G-reg TB20 having a higher ceiling

I would call the ceiling the altitude where the plane won’t go any higher. The stall warner should also be on continuously. One would not fly there but that’s not the point Actually I have flown up there at times, trying to stay above some wx, as some here may remember

If I ever transfer my plane to G-reg (extremely unlikely since the only reason would be losing my medical, but Brussels is screwing the NPPL option next month, for certified aircraft, so my only way to fly would be to go homebuilt, or recruit a PPL/IR RHS occupant) I can peel off the “Flight in icing conditions prohibited” placard In fact the whole STC status would be interesting… CAV authorise their US STC for EASA-reg via some weird route involving an inspection by some local inspector.

I find the Vy speed at absolute ceiling to be about 70 KIAS while the stall speed is 48 KIAS!

I think the 48kt is Vs2 i.e. full flaps. 70kt is probably close to Vs0 for a C172. The TB20 Vs0 is not much above that.

Administrator
Shoreham EGKA, United Kingdom
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