Wing Wednesday 12/02/2020

[Krakin 6,013]

 

[Krakin 6,013]

Just gorgeous!

[aleex 551]

Cold as winter ❄️ 

[suncoastflyer 685]

That ice buildup 😮

[Quasimodo 505]

looks great, only, I think, if there is ice on the wings there should be ice on the fuse too?

Edited February 13, 2020 by Avidean

[bonchie 2,305]

39 minutes ago, Avidean said:

looks great, only, I think, if there is ice on the wings there should be ice on the fuse too?

Not necessarily.

[poplar 39]

“Having a rough week?” 

It’s almost like Asobo know the pain and anxiety non invited Alpha testers are feeling right now. 

Edited February 13, 2020 by poplar

[Claviateur 789]

Looks really good and I admire again these little details Asobo like to pay attention to. 

[Chock 17,769]

15 hours ago, Avidean said:

looks great, only, I think, if there is ice on the wings there should be ice on the fuse too?

Sometimes yes, but generally speaking, the cold temperature of the fuel in the wings, as opposed to the higher temperature of the fuselage from things such as radiated heat from its cabin, engine cowling, avionics and AC vents etc, means visible ice is far more likely on the wings, whereas there's more likely to be invisible ice glaze on other bits of the airframe. This is important to know;  just because you cannot see very obvious evidence of ice, it does not mean it is not there!

Rough-looking ice on a wing is most typically caused by the phenomenon known as cold soaking. This is when prolonged flight in a cold region makes the fuel in the wing really cold, and it remains so even if the aeroplane has then passed into a region where the ambient temperature is pretty high. What happens then, is moisture in the air freezes instantly when it comes into contact with the very cold wing surface, particularly if the moisture happens to be in the form of supercooled water droplets (water at below freezing, but still in a liquid state). When ice like this forms (typically on a wing), it is called rime ice. It looks rough in appearance because when the water droplet smashes into the wing, splashing about as it freezes, this creates a lot of air pockets and frozen splash patterns. Fortunately, because of the crystalline structure caused by it freezing whilst impacting on the airframe, rime ice is brittle, so it can usually be cracked off by de-icing boots or heated leading edges, especially since it tends to be on the front of the wing where those de-icing boots and heaters are located.

The possibility of cold soaking incidentally, is why you see aeroplanes on fast turnarounds being de-iced or anti-iced at airports, even when the ambient temperature seems like it is nowhere near low enough to warrant de-icing, because they can be on the ground and taking off again in as little as 25 minutes, which is not long after having been in really cold temperatures where the fuel has dropped to a very low temperature too, making the formation of ice on the wings from quite warm rainfall easily possible as it contacts the freezing cold wing skin. It's worth noting for those who are into all this kind of thing in their flight simming, that anti-icing and de-icing fluids are usually good for about 45 minutes tops. After that, you'd need to do it again for it to be effective.

Conversely, on other parts of the aeroplane, the moisture in the air might not necessarily freeze instantaneously upon contact with airframe, instead it can remain in its liquid state for a few seconds, causing it to run back along the fuselage, gradually freezing as it runs back. This allows it time to smooth out and spread, making it freeze as more of a glaze, which with no rough surfaces, can be difficult to see. This sort of icing is called clear/glaze ice and unlike rime ice, it is not brittle.

Then you have something known as SLDs (supercooled large droplets), which can cause mixtures of those two types of icing, although in the case of these, the word large is a bit misleading since an SLD is defined as any droplet larger than 0.05mm in diameter, i.e. SLDs are still pretty small. The problem with those little buggers however, is that their comparatively large mass prevents them from being deflected over and away from a wing's pressure wave, as is the case with regular moisture drops in clouds. This means SLDs can pass the leading edge de-icing boots of a wing, but then hit the wing surface behind the de-icing boot and because of their size, freeze as they run back, forming clear/gaze ice and rime ice, which the de-icing boot can do nothing about.

This is why it is important to not fly through too much cloud for prolonged periods in freezing rain conditions, and certainly not without turning every bit of de-icing protection you have on your aeroplane on full. It's also why the ATR-72 and the ATR-42 both had their de-icing boot designs modified to operate further back along the wing than they originally did on the first variants, and most of those early models were similarly modified too. This was as a result of a few accidents with the type when flying in freezing rain.

Back with that picture though, despite the fact that in reality if there was that much rime ice on the upper surface of the wing of an aeroplane, it would probably be in an uncontrollable spin, I am nevertheless pleased to see them adding stuff like that, even if it is a bit over the top visually.

Edited February 13, 2020 by Chock

[FDEdev 955]

16 minutes ago, Chock said:

It's also why the ATR-72 and the ATR-42 both had their de-icing boot designs modified to operate further back along the wing than they originally did on the first variants, and most of those early models were similarly modified too. 

Back with that picture though, despite the fact that in reality if there was that much rime ice on the upper surface of the wing of an aeroplane, it would probably be in an uncontrollable spin, I am nevertheless pleased to see them adding stuff like that, even if it is a bit over the top visually.

One of the main drawbacks with boots is the timing. If you use them too early the ice will freeze over the inflated boots and further cycles will not break the build up. If you use them too late, the boots will be unable to inflate at all.  Flying in icing conditions with a jet is one very the big advantages over a turboprop. 

The ice build up on the screenshot doesn't look excessive IMO and it definitely wouldn't throw the aircraft into a spin. There have been various  contamination tests with large styrofoam blocks glued onto upper wing surfaces to test the loss of lift/controllability.

Deicing is overrated anyway 😉    

 

[Chock 17,769]

26 minutes ago, FDEdev said:

One of the main drawbacks with boots is the timing. If you use them too early the ice will freeze over the inflated boots and further cycles will not break the build up. If you use them too late, the boots will be unable to inflate at all.  Flying in icing conditions with a jet is one very the big advantages over a turboprop.

That's called ice bridging. But you know there is some debate about that right? The NTSB issued a Safety Alert on this following the investigation into the crash of - if memory serves - a Metroliner, where the crew delayed using their de-icing boots, which was apparently their airline's recommendation, and as a result of their delay in doing so, the airliner crashed when the icing build up caused an unrecoverable aileron deflection. Here is the NTSB's SA on the subject which came about as a result of the research the FAA and NASA did as part of that particular crash investigation:

https://tuttoqua.files.wordpress.com/2009/07/sa_014-ntsb.pdf

Apparently the FAA and NASA tried to replicate the condition of ice bridging and couldn't do so. They stopped short of claiming the phenomenon of ice bridging was a myth, but they do say that it is very rare and that using de-icing boots immediately is their recommendation. That said, more than one manufacturer disagrees with the recommendations on this, for example, Cessna specifically state that the de-icing boots on their Citation 560 work better after there is some build up of ice rather than using them immediately, so they recommend allowing that to occur.

Edited February 13, 2020 by Chock

[Quasimodo 505]

@Chock Let me commend you on your post. All sounds vaguely familiar from my ground school days. I wish I had your memory for the details. 😁

[Quasimodo 505]

Let's not forget that to this day despite the sophistication of aerodynamic there is still no conclusive scientific explanation as to why lift is generated at all.

Don't ask me explain it:

https://www.scientificamerican.com/article/no-one-can-explain-why-planes-stay-in-the-air/

[Chock 17,769]

50 minutes ago, Avidean said:

Let's not forget that to this day despite the sophistication of aerodynamics there is still no conclusive scientific explanation as to why lift is generated at all.

Lift is generated by sticking your thumb out when a car approaches.

Edited February 13, 2020 by Chock

[threexgreen 3,160]

5 minutes ago, Chock said:

Lift is generated by sticking your thumb out when a car approaches.

Which is why lift is generally a very unreliable phenomenon.