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Ultimate anti-icing ?

One should take the heat somehow from the hot exhaust gases, at least with piston engines (?), that would not reduce the performance.

That’s exactly what this patent is about. But it lacks the calculation of the heat required as opposed to the heat that can be extracted from the exhaust gases. I am a bit skeptical there. And what if one flies with reduced power, e.g. during descent? Many light jets don’t produce enough bleed air for de-icing during descent unless one descends with power against the speed brakes or extended gear.

EDDS - Stuttgart

Yes, but it leads to the obvious Q of why this has not been done before. Let’s face it, none of the existing de-ice systems (boots or TKS) are good engineering solutions. All have major issues.

Also I bet that – unless this really is totally hopeless – there is prior art, but nowadays you can patent anything provided it is fairly obscure, or you put in enough conditions to make it unique.

Administrator
Shoreham EGKA, United Kingdom

Yes, but it leads to the obvious Q of why this has not been done before

I know that some liquid cooled engines use(d) the leading edge of the wings as radiator. But these were fighter airplanes with 1.000hp engines and plenty of excess heat (e.g. the Hawker Tempest). In the nineties, a company called “Orenda” was developing a 500-800hp liquid cooled engine aiming at the piston twin (C421, Piper Navajo) and small turboprop (King Air 90, Piper Cheyenne) market. They also claimed that their radiators could replace the de-ice boots (or at least part of them). But the project was cancelled before the first one flew so we will never know if it would have worked.

EDDS - Stuttgart

The Tempest had the radiator faired in the wing root leading edge, but it didn’t (nor could) have any effect on deicing.

The Orenda engine is still alive, called TRACE.

The Orenda engine is still alive, called TRACE.

That’s good to hear. When I used to fly the C421 I was really wishing for an Orenda/Trace conversion. More power, liquid cooling, no more constant fear of shock cooling the engines, faster warm-up time in winter. But as it looks, they are right now mainly focusing at the ag-plane market. In their list of aircraft conversions they have a Kingair 90, but google doesn’t show it anywhere.

EDDS - Stuttgart

Liquid-cooled? Blasphemy!

I doubt that there would be enough heat in the exhaust of a piston engine. Not in a small TIO360 as it isn’t enough to keep the cabin above freezing at -32C outside.

EGBE - Coventry, United Kingdom

The other issue with exhaust gas heat recovery is the corrosive byproducts, due to the low temperature of the final exhaust.

This is a big problem in condensing boilers. You get a nasty acid dripping out at the end, and it has to be piped somewhere suitable. With a domestic boiler, UK regs, it can go into the ground but has to be at least 5m away from the foundations. It is OK to run it to the sewer, which in many cases is impractical.

With an airborne aircraft, one would just let it drip out, but you would have to keep it well away from any part of the airframe, which is difficult. And it will make a nasty stain on the hangar floor.

The exhaust-jacket cockpit heater on GA planes recovers only a tiny % of the exhaust heat. It’s a very poor heat exchanger. I reckon it collects maybe 5-10%.

I am sure many people have been up this path during decades past, without having written about it on pilot forums…

Administrator
Shoreham EGKA, United Kingdom

I am sure many people have been up this path during decades past, without having written about it on pilot forums…

You bet! Just think about those multi-engined bombers of WWII or the big piston engine powered airliners of the 1950ies. They were designed by pretty smart people. If exhaust heat anti-ice would have been a suitable option, they would have done it that way. Instead, they fitted de-ice boots.

EDDS - Stuttgart
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