Electrical Windshield Heat

[HPNPilot1200]

I was flying a trip in the Phenom 100 yesterday and noticed that forward visibility was somewhat blurry with the WHCU's (windshield heat control unit) on. We turned them off briefly and noticed that items in the windscreen began to appear much more clearly. Other owners and operators have reported similar observations but I was curious as to what type of interference or design characteristic would cause this. Any experience or ideas regarding blurry vision with electrical windshield heat?

Not such a big deal up in the flight levels, but down low looking for traffic and transitioning to final approach it was somewhat distracting.

 

[TMetzinger]

My guess is that the heat is making the window material expand internally a bit - altering it's optical properties.

 

[kgruber]

Many heated windshields are distorted. Some are not.

 

[Teller1900]

The 1900 was the same way. At some point on final, we'd always have to ask the other guy to "turn the blurry vision off." Neither the Q nor the Saab do it, though, and they both have similar heating systems (I think). I don't know why, but not at all uncommon I don't think.

 

[HPNPilot1200]

The 1900 was the same way. At some point on final, we'd always have to ask the other guy to "turn the blurry vision off." Neither the Q nor the Saab do it, though, and they both have similar heating systems (I think). I don't know why, but not at all uncommon I don't think.

I almost felt like cycling the windshield 1 & 2 switches in the Phenom was like going to the eye doctor, "which is clearer, 1 *flips gadget* or 2?"

 

[Tristar]

The King Air does that too. We'll turn the "blurry vision" off once we're out of ice. I'm under the understanding that the heat distorts the windshield. It has to get very hot!

 

[Let'sgoflying!]

It has to get very hot!

In some a/c if you turn the w/s bleed air on while stationary, it gets so hot it will melt a hole in the perspex. "There, now I can see just fine!"

 

[tonycondon]

421 was the same way

 

[HPNPilot1200]

The King Air does that too. We'll turn the "blurry vision" off once we're out of ice. I'm under the understanding that the heat distorts the windshield. It has to get very hot!

Interesting. The WHCUs on the Phenom regulate window pane temperature automatically by only heating when the pane is below 95ºF and turns off when it reaches 110ºF. At least it's not a noisy bleed air system though the engines are probably not big enough to provide that type of support. We don't even get a hot wing just silver painted polyurethane boots which look pretty funny.

 

[Tristar]

We have a fair amount of icing "toys" on the king air. We turn the "hot five" on every time we take off whether we're in IFR or not. It's always good to be prepared. Windshield heat isn't part of that. I always thought it was interesting how the hottest part of the windshield is in cockpit center. I would have thought it would have been directly in front of the pilot/copilot. The weirdest feeling is when ice departs the prop tips and hits the cabin. The first time I flew in ice in the king air I kept hearing this, "thud!" "What was that?!" "Oh that's just ice from the props." I keep wondering if I'm going to walk around the plane someday and see huge dents from that stuff.

 

[Everskyward]

Interesting. The WHCUs on the Phenom regulate window pane temperature automatically by only heating when the pane is below 95ºF and turns off when it reaches 110ºF. At least it's not a noisy bleed air system though the engines are probably not big enough to provide that type of support. We don't even get a hot wing just silver painted polyurethane boots which look pretty funny.

The King Air (at least the BE-20) is just about the same. Here is the page from the training manual.

I remember the blurry vision effect in the King Air. The Hawker 800 and the CE-680 also have electric windshield heat but I've never noticed any distortion. The windshield heat in those airplanes is always on, though. It is not something you turn on and off depending on conditions. The Lear 35 and 55 had the bleed air system which I thought was really inefficient, especially at keeping condensation from forming in humid conditions. Not to mention the fact that it was pretty noisy.

 

[taters]

Interesting. The WHCUs on the Phenom regulate window pane temperature automatically by only heating when the pane is below 95ºF and turns off when it reaches 110ºF. At least it's not a noisy bleed air system though the engines are probably not big enough to provide that type of support. We don't even get a hot wing just silver painted polyurethane boots which look pretty funny.

I went on a Phenom demo in the fall and thats the first thing I noticed. "Hey look at the hot wing!...ohh never-mind." The 300 has them(hot bleed) but really an entire different class of jet where it would be an expectation. That phenom is a hell of a machine, competitors not even close IMO.

 

[HPNPilot1200]

I went on a Phenom demo in the fall and thats the first thing I noticed. "Hey look at the hot wing!...ohh never-mind." The 300 has them(hot bleed) but really an entire different class of jet where it would be an expectation. That phenom is a hell of a machine, competitors not even close IMO.

The 100 boot used to have a big black dot on the outboard portions so you could tell if ice was forming but that has since been removed by Embraer (maybe they changed the color of the boot slightly). The 300 is really a different aircraft all together though SimuFlite and Embraer both say its a 3 day transition course to upgrade from the 100.

We departed just under 9800# with 2200# of gas and ISA -27 and climb rate was fantastic. It was a short hop so we leveled at 10,000, but I'm looking forward to seeing what kind of TAS/fuel burn we get up high. From what other Phenom 100 owners/operators have told us, it seems to like the mid to low 30's.