Aviation technical quiz

[Nick - A2A]

Yeah, there's a certain felicitousness in English too: retractable keels → retractable wheels!

What might that object be?

This could take a while! Wonder if it's related to the Sabre's nose intake being pretty prominent. Maybe some form of apparel like hats (uniform caps anyway) because they had a habit of getting sucked in?

Nick

[Levkovvvv]

Nick, you are officially psychic Yes, the standard issue army cap (titovka) had a metal red star at the front of it and it wasn't really securely fastened to your head, so they got sucked in a lot and the metal badge damaged the compressor blades. They banned all headgear at airports except for helmets which had chin straps.

[Nick - A2A]

Hey - lucky guess! I had a hunch it could have something to do with the unusual intake arrangement on the F-86 and F.O.D. Head gear seemed a good starting point; in fact, I wondered if the "get your thinking caps on" remark in your question was a little clue.

Anyway, those titovkas look pretty thick and warm. Bet that order was mighty popular out on the flight line during the freezing winter months!

Cheers,
Nick

[Levkovvvv]

Yeah, I used thinking caps on purpose, might have been to obvious. They were thick but they didn't offer any real protection. That photo might have been misleading, this is the real fit of those caps.

As you can see, they don't cover your ears, and they were worn for ceremonial purposes all year round, all day, and not for protection from the elements. There are reports of enlisted men loosing hair due to wearing that thing every waking moment. In the winter, security personnel wore helmets with chinstraps that had sort of a hood over them that reached to the shoulders and ground crew either wore nothing or in extreme conditions, "mountain unit caps" which had ear flaps, chinstrap and a peak.

[AKar]

Now, to the fun part. Shortly after arrival of the Sabres in 1956, a decree was passed banning the use of a certain object to all pilots, ground crew, and security personnel stationed on airports where the jets were located.

To continue the fun part, what specific routine service item on the MiG-21 required specific permits of the crew to handle in Finnish service? (At least the story goes, but I can't figure a reason why it shouldn't be true!)

-Esa

[Levkovvvv]

Oh come on, not fair, the engine was maybe the only part of Finnish mig-21s that was stock, they replaced all the flight instruments for western ones, added chaff and flare pods, reconnaissance pods, removed radars, and probably a ton of other stuff I can't think off. Since I don't know the real answer, I'll try with the funny ones.

Maybe the Kilju brewing containers the pilots hid in the nosecones of the reconnaissance versions that had the radar removed? I assume ground crew shouldn't touch those without permission because they don't know how long they have been sitting, and judging by the rate of alcohol consumption in all the worlds airforces, those would be a routine service item

(on a related note, mig-21 radars were cooled with alcohol which had to be topped off regularly, it might have something to do with that? )

[AKar]

FAF MiGs were stock in perspective to my question, no details relevant to this were altered, to my knowledge. And you gave enough of tip so that I won't give another one!

MiG-21 is relatively high-performance fighter, but somewhat highly doctrine-dependent as the fighters of the era were. As a war plane, I'd rate it significantly above the contemporary F-104, and much of the century-series; almost as if it was an F-16 a couple of decades earlier. Of course, those were fast times of advancement in the field of aeronautics, and the later airplanes quickly outclassed the 21 as platform.

Edit: To be honest, I am not sure if the windshield de-icing I was after is a point worth of pursuing, as you clearly got the idea! So let us say that's correct. By the service instructions, these airplanes took in some stiff ethanol into their anti-ice system (windshield), and as that happened to have some more entertaining uses and naturally high proportion of deficit, the story goes it was soon determined arguable to rise certain regulation on the folks having access on the stuff.

-Esa

[Levkovvvv]

It was probably the same stuff they used for the radars. You had about 20ish minutes of radar use before you needed coolant refilled. O am guessing they serviced it even more often then the windshield deicing fluid because in an interceptor, you use the radar every time but encounter icing conditions some of the time.
But the whole situation is quite common in aviation. While Yugoslav Airlines had flights to New York, portable oxygen bottle valves were replaced extremely often because the oxygen would mysteriously leak out. That had nothing to do with the fact that the crew had a bit too much American whiskey which wasn't readily available back home and than breathed in O2 to help sober them up, which would show on the pressure gauge so they brought a bottle of whiskey back to the mechanics who would write the valve off as defective, replace it and refill the tank.

[AKar]

A little background.

Pretty often one runs into a sim-related discussion regarding icing (not speaking about carburetor icing this time!). It is one of the least understood issues in the world of simulation, as its effects are certainly very difficult to get right. This reflects into discussions: often icing conditions are considered as if they were an instant killer for a non-FIKI (Flight Into Known Icing) certified airplane, but many also believe that a flip of a switch in a FIKI-certified airplane practically relieves from the issue. It appears that many even live in a believe that the trailing-edge control surfaces (ailerons, elevator, so on) are generally heated.


Okay,

To gain perspective: What surfaces of Airbus A350 (obviously a FIKI-certified airplane, used as a modern example) are ice-protected?

An easy one of course if you know it, but if you think the background explanation applies to your understanding of the icing issue, google it.

-Esa

[Levkovvvv]

In a non FIKI certified airplane, ice will not be an instant killer and you will often have some sort of ice protection system on larger airplanes, but that system is enough to get you out of icing conditions safely and not enough to permit you to continuously fly in icing conditions.

On a FIKI certified airplane, systems are in place to protect you from ice, but those systems have limits, and they use electricity/bleed air which means they use fuel which means that you should avoid known icing conditions whenever possible. And I don't believe anyone heats the trailing edges, actuators are strong enough to break off any ice that might form, and airflow is usually already turbulent enough by the time it reaches the trailing edges that ice probably wouldn't make any difference.

As to the answer to your question, I'll use the term surfaces loosely to refer to all areas that are heated:
We'll start with the 2 lighted icing indicators that are located under the windshield in full view of the pilots, 2 icing probes located on the underside of the cockpit, probes and ports of the pitot-static system, slats 3, 4, and 5 on each wing, air intake lip on both engine nacelles, both windshields, both forward and both aft lateral windows, and various components of the potable and waste water system that I am currently too lazy to list. And yes, maybe the question would be better suited to someone who doesn't have the A-350 Technical training manual laying around the hard drive

[AKar]

Yep, probes, engine intakes, windows and such, but aerodynamically speaking, three middle slat panels of each wing are ice-protected. Nothing more. In A320, the outer three slat panels are ice-protected. In 737, three inboard slat panels are ice-protected. None of the tail surfaces for instance are ice-protected in none of these.

Trailing surfaces are not in general exposed to icing. In cases where they can end up to be, like flaps, there are typically rather common sense limitation in place: many manuals tell one to avoid extended flight in icing conditions with flaps extended, and to not retract the flaps after landing to avoid damage on them. If a control surface does have a portion facing into the airflow, it may have electrical heating: this is often the case with balance horns on turboprops. Most fighter jets only use probe and inlet ice protection, with no aerodynamic ice protection whatsoever.

There are a lot of myths regarding icing and winter operations, one of such is that the ATR for instance is particularly vulnerable to icing conditions. The thing is, due to their operating altitudes and lowish speeds, all turboprops are inherently vulnerable to icing, and are actually more comprehensively ice-protected than many jets, as they need it more. In icing conditions, ice will accumulate on any airplane, and the design has selected the most critical parts to be ice-protected and considered the accumulation on the other parts as acceptable in moderate amounts. That's why approach and flaps speeds are generally altered when anti-ice is used: to take into account the penalties by icing on the surfaces. Typically no system is intended to defeat severe icing for any extended period of time.

-Esa

[Levkovvvv]

The thing about turboprops and ice should be quite obvious to sim pilots, as when you sit in a cockpit of a q400 or a js4100 or a c-160 compared to lets say a 737 or an a320, the proportion of overhead panel dedicated to ice protection is substantially larger on the turboprops. But then again people usually associate aviation icing with walking up to their car in the winter and finding every exterior surface encased in ice

[AKar]

Yeah, another interesting topic is different vulnerability to ice in between different wings.

If Active Sky folks or someone could provide reliable icing information and the airplane developers could develop a proper icing simulation using that data, it would be absolutely great for simulated winter flyers! What I'm afraid though that what happens is like with storms...overdoing it with every occasion trying to kill you.

-Esa

[Levkovvvv]

I think that majestic q400 has a somewhat acceptable model of icing, but sadly it is one of the very few that do. And developers often overdo some effects to make up for the lack of physical sensation you experience when flying from your armchair as opposed to the real thing. Great example would be various cockpit sounds that people expect to hear that could never be heard in the real airplane. There was a rather heated discussion about flap sounds in the cockpit over on the aerosoft forums a few weeks back. Mathis said they basically put in the audible flaps in cockpit because people want them, not because you can hear it in the real plane.

[AKar]

I think that majestic q400 has a somewhat acceptable model of icing, but sadly it is one of the very few that do.

Yeah, though icing is still quite localized phenomenon; I'd expect it to work best when the weather engine knowledge of airplane being in the cloud or fog (as used for the appropriate graphics effects) could be utilized. That way you could use your judgement to stay out of icing. Though speaking of weather engines, as of now, any airport with TS in its METAR is all but unusable with AS16 unless you tune down the settings; I'd hate that to be the case with icing as well, as it is pretty localized, and even a shallow freezing fog layer makes an ATR look like this (the accumulation on the very tip of the radome is unfortunately almost not visible in this). I'd hate to see this applied to "general area" in the sim.



-Esa