Violent manoeuvring breaks the Artificial Horizon indicator?

[Extreme_One]

I don't know if this is a bug or not??? Never seems to happen in IL21946

In the Hurri and the Spit, I'll be pulling violent manoeuvres and level out and my AH will be totally skewed and display as if I was hard banking.

Is this a bug or a 'feature' whereby the AH was sensitive to this kind of manoeuvring in RL?

[DC338]

No bug. The gyro's are toppled by violent manuevring. British aircraft are not fitted with a caging mechanism (holds the gyro in place) at this stage of the war and so after periods of heavy manuevring you need a fair stretch of straight and level in order for the auto leveling function to work and get your AH back.

[Sauf]

ahhh, its the little things like this that make this sim great!

[Extreme_One]

No bug. The gyro's are toppled by violent manuevring. ...

Thank you. Just goes to show what an awesome sim this is.

[Viper2000]

The way this works is that the gyro is biased to self-erect.

So if you give it about 5 minutes, it will return to showing level flight.

This means that if you were to hang around in a turn for a long time, the artificial horizon would gradually return to level flight despite the fact that the turn was still continuing.

The other thing to remember is that these old instruments don't seem to have failure flags. If the suction or electrical power source driving the gyro dies then obviously the second law will take its course, and the gyro will slow down.

The first you'll know of this is when it starts to nutate (ie wobble like a spinning top that's about to fall over). Then it'll topple, and you'll have false indications. Without failure flags, the only way to work out that the artificial horizon has failed is to cross-check it against the other instruments; hence the requirement for a good instrument scan.

This really makes instrument flying difficult. You can still proceed partial panel with the turn & slip (assuming that it has an independent power source), but it's not fun. You have to make a real effort to ignore the failed instrument, and you also have to infer what it would normally tell you from the remaining good instruments. In fact, IRL it's a really good idea to carry some scrap paper and tape around just in case; that way, if an instrument does quit on you then you can at least cover it over with a bit of paper so that the false indication doesn't distract you.

This might be quite a nice little easter-egg type feature if somebody could code it up. So you'd right-click an instrument and get the option to cover it. Then you'd suffer anthropromorphic pain for a few seconds before the dead instrument was obscured...

[During my PPL I had to do some sim time, and since the sim was IFR only I found myself very much out of my comfort zone flying blind. The instructor was bored and feeling evil, so he tried to "kill" me. First I lost an engine, and then when I survived that he started failing my instruments. I ended up trying to shoot an ILS partial panel with one engine and 25 knots of crosswind, and I can tell you that somewhere along the line that sortie I started to sweat...]

In addition to the Artificial Horizon toppling, you will probably also topple the turn & slip and the DG if you chuck the aeroplane about. The magnetic compass will also be spinning all over the place for a while. So after aerobatics or combat you're back to pure VFR for probably 5-10 minutes until you work out where you are and what you're doing. This can make you very vulnerable if you're not careful.

It also means that it's sensible to work out alternative means of navigation, especially over the channel. I suggest using the sun and a wrist watch to work out which way is North. Then you can at least head for the correct coastline.

Once you get there you can then switch to visual navigation.

Also note that IRL you get static port position errors on the ASI and altimeter. These can make life really difficult. For example the Merlin Spitfires have VNE of 450 mph EAS; the position error is about 20 mph at this speed, and therefore the acceptance tests involved diving to 470 mph IAS, which is a slightly unnerving concept.

The other classic, post war, was that the English Electric Lightning would tend to under estimate altitude at transonic speed. This meant that low level intercepts over the sea were routinely flown at negative indicated altitude. And they did this at night. Balls Of Steel!

[AndyJWest]

I suggest using the sun and a wrist watch to work out which way is North. Yup. I seem to recall that the RAF got hold of a Fw 190 from an unfortunate Luftwaffe pilot who got this wrong...

...the English Electric Lightning would tend to under estimate altitude at transonic speed. This meant that low level intercepts over the sea were routinely flown at negative indicated altitude. And they did this at night. Balls Of Steel!

And presumably, underwear of asbestos. ;)

I'm really looking forward to getting into this sim, and messing things up in ways I'd never have thought of before. I think that some of those who complain about how difficult it is to deal with all the complexities should remember that only the most proficient were selected to fly, and then it took a long time to learn - if you lived long enough.

[bolox]

well if you really broke it, your crew chief would probably throw this book at you;)

http://www.mediafire.com/download.php?o4gr62l66bij90l
(sperry ah repair manual)

[whoarmongar]

The unfortunate FW-190 pilot did get a bit lost, somehow he managed to fly NW thinking he was going home, he crossed the Bristol Channel, thought it was the English channel, and landed in south wales. Thus handing a nice FW-190 to the British.

[Extreme_One]

The way this works ...


Very informative, thank you.

The other classic, post war, was that the English Electric Lightning would tend to under estimate altitude at transonic speed. This meant that low level intercepts over the sea were routinely flown at negative indicated altitude. And they did this at night. Balls Of Steel! :eek: That's incredible.

[IvanK]

AH precession (not as a result of Gyro toppling) is overdone. AH errorrs after extreme manoeuvering (i.e. Gyro limits excedded) is well done. There are 2 possible AH versions the MKI and the MKII each has slightly differrent limits. the limits as detailed in the AP1257 are:

MKI +-60 degrees in Pitch, +- 90 degree in Roll
MKII +_45 degrees in pitch, +- 360 degrees in roll

Following a a complete topple the AP1257 states that up to 10mins in 1G unaccelerated flight may be required for the AH to erect. In addition these AH also exhibited acceleration errors that required pilot allowance in the pitch axis. Typically on take off acceleration resulted in the AH displaying an artificially higher than correct pitch attitude. To prevent settling back to terra firma in an IF Take off pilots typically added an "extra Bar width" in pitch until the climb IAS was achieved. With no linear acceleration Pitch info was reliable.

There is good video of the degree of precession that occurs in an In cockpit and external cockpit split view of a Hurricane MKI Air display. This aircraft is equipped with original instruments MKII AH it seems. This is a 10 min display that includes many rolling manoeuvres and Pitch manoeuvres. The video is in the hands of the devs.

[Russkly]

The way this works is that the gyro is biased to self-erect.

So if you give it about 5 minutes, it will return to showing level flight...

V. interesting!

Does this account for the DI being constantly out too then?

I'll do some more testing, but IIRC it's out by up to 180 deg. even during level flight and not after manoeuvring.

R

[senseispcc]

No bug. The gyro's are toppled by violent manuevring. British aircraft are not fitted with a caging mechanism (holds the gyro in place) at this stage of the war and so after periods of heavy manuevring you need a fair stretch of straight and level in order for the auto leveling function to work and get your AH back.



Sorry,

But in a book "First light" autor Wellum Geoffrey he write about caging and uncaging instruments (most of the time the artificial horizon), I do think they had this possibility.

Have a nice game.

[IvanK]

Sorry senseipcc, I suggest you re read First light I think you will find the only Gyro caging mentioned was during training when his mate pranged after take off during night flying. He took off with the AH caged .... that was in a Harvard.

Spits and Hurricanes in 1940 did not have the ability to cage the AH.

[jimbop]

AH precession (not as a result of Gyro toppling) is overdone. AH errorrs after extreme manoeuvering (i.e. Gyro limits excedded) is well done. There are 2 possible AH versions the MKI and the MKII each has slightly differrent limits. the limits as detailed in the AP1257 are:

MKI +-60 degrees in Pitch, +- 90 degree in Roll
MKII +_45 degrees in pitch, +- 360 degrees in roll

Helpful, thanks.

[Pist-N-Broke]

Sorry senseipcc, I suggest you re read First light I think you will find the only Gyro caging mentioned was during training when his mate pranged after take off during night flying. He took off with the AH caged .... that was in a Harvard.

Spits and Hurricanes in 1940 did not have the ability to cage the AH.

Why would a Harvard trainer have a caged AH, and not a front line combat aircraft like a Spit or Hurri?

[DC338]

Why would a Harvard trainer have a caged AH, and not a front line combat aircraft like a Spit or Hurri?

Because one was built in the US with US instruments and the other was built by the British. Also these were originally built as day VFR fighters. Partial panel is a blast;)