I'm assuming you're reply with the summary was meant to be totally flippant, either that or you really didn't get much out of what was posted here as you were expecting people to agree with some other point perhaps "There is no reason, it's ridiculous" possibly to backup some ridiculous argument you've had, otherwise why else ask here instead of asking the people you are studying with and/or people you're paying to train you.

You're going to make an excellent Pilot mate.

Not totally flippant but certainly tongue in check. Yes, the question arouse from a discussion at the flight school. Collectively we couldn't find any compelling logic for a) the extra requirements for charter work and b) assuming the logic is a guard against inadvertent IMC, why the T&S rather than AH. (You would have to be very unlucky to enter IMC just as your vacuum packs it in.)

I my view, none of answers so far have really nailed why the regs are they are. The closest answer I can surmise is that the requirement goes back to days of K-S when T&S indicators were more common/affordable than AHs.

Perhaps more to enable some of the older aircraft around the traps that didn't have things such as AH's, to still be able to perform day VFR charter.

morno

You're probably right to a certain degree. It's possible those Regs were designed around a time when it may not have been possible to have an Electric AH that was reliable enough, perhaps these days it may even be possible to get an exemption to replace your T+B with an Electronic AH but I can't really see the reasoning, being an electrically driven mechanical device that would most likely have to be permanently activated with the aircraft electronics, in the event of an alternator failure, would this be an unacceptable extra drain on the battery compared to a T+B?

The other reason is that the T+B would be, IMHO, superior to the AH in the event of your Primary AH becoming U/S for the exact reason that others have mentioned that you can execute a pretty damned perfect 180 with just the T+B and your Watch which is not as easy to do with the AH. If you're in the soup and the AH goes then presumably your DG is also going to be gone as well and trying to use the damned Mag Compass when underpressure and with it bouncing around does not sound as appealing to me as starting a turn on the top of the minute then rolling out when it gets back to the top of my watch!

A T+B also has the upside of being able to keep your aircraft in balance which an AH doesn't do which is for passenger comfort and generally speaking I've had enough AHs start to go a bit wonky on me but I can't say I have ever seen a T+B that wasn't dead on accurate.

In a twin engine as well, in the event of an engine failure, it is far easier to just step on the damned ball and get it centered to correct for the yaw.

You'll also find that just about every aircraft has one installed, infact I've personally never flown an aircraft that didn't, so why bother to rewrite regs just for the option of removing something that everyone already has, I can't see why you would remove it and bringing back to my earlier point I've never seen one fail so I'd presume they last a really really long time and hardly ever require replacement so if it ain't broken, don't fix it!

Same goes for the regulations, if there was something better out there to replace it with and the industry was clamouring for it then they might look at it, but as the point has probably never been raised and there is apparently no problem to fix, why fix/fiddle with a regulation that isn't broken?

Thanks Ixixly. However, my point is that the regs say that for VFR I'm not required to have AH just a T&S (plus the other primaries). So the answer is not in case my primary AH fails.

I have considered passenger comfort as a possible answer but the same rules applies to Airwork without passengers.

Also, I'm not suggesting anyone remove any equipment. My question is no more than an attempt to understand the reasoning behind the regulations. (Notwithstanding many of comments on this forum, I believe that most of requirements we have are for good, if sometimes obscure, reason. Naive perhaps.)

xxx,

I am thinking you mean Norfolk Island. Lord Howe in a 737 would be something Special !!!!!

Groggy

A 737 at Lord Howe?

I'd love to see that :}

Geographically challenged is the word ! Give me a break, the are both islands and in the middle of the same ocean :ok:

Norfolk does sound better ;)

I see your point, in that case it comes down to Inadvertent entry into IMC, in which case having an AH is less critical than having a T+B, as we're all taught if you enter into Inadvertent IMC then you make a 180degree turn back onto a reciprocal heading, this is done by making a rate one turn which is indicated by your T+B but not on your AH (Yes, I know you can work it out but really that's the last thing you want to be doing).

Basically for VFR Flight you shouldn't 'require' an AH for a normal flight as you are "Visual" so therefore having a regulation that requires you to have an instrument that isn't required for your normal flight wouldn't be right, but should you enter into Inadvertent IMC then you require a means of getting back out of it which is why you use your T+B to turn around not an AH. So therefore you don't REQUIRE an instrument to make a flight Visual but you DO REQUIRE an instrument to get you back to Visual.

I believe TC type instruments (tied gyros in general) are less susceptible to failure than AH instruments (earth gyros), and are designed to make it easy to detect a failure when it does occur. We've all flown VFR with slightly wobbly AH's, but hopefully less often just ignored a flagged TC or T&S.

Ted, I'm not sure you're considering the two main implications here. Disregard the odds of the instrument failing just as you enter IMC, and consider:

- It is cheaper to maintain a TC over the long term, than an AH, and

- A pilot is more likely to detect (and have repaired) a failed gyro straight away if it has a simple failure flag on it, as opposed to being a little wobbly at times.

One is important to the operator, and the other to the regulator. Current law covers both bases.

In terms of safety, once in IMC, an AH is safer than a TC. Difficult to argue otherwise I think Ixixly...

Oktas8 Agreed on the failure likelihood of AH vs T+B, my comments in regard to the use of either AH or T+B in IMC were only meant to be taken in regards to the situation of a VFR Aircraft inadvertently entering IMC and having to turn around safely onto a reciprocal track to return to VMC with a Rate 1 turn onto a reciprocal track being easily achieved with a T+B and your watch.

Of course it can also be done on the AH at an acceptable Bank Angle and using the DG but I'd probably trust the T+B more than an AH which isn't necessarily designed, tested or maintained to an IFR standard and is known to be a bit askew, plus if you rely on the AH and it isn't quite up to scratch like you thought then you might find yourself trying to maintain a turn on the AH which is actually based upon an AH that is toppling without you realising leading to far bigger problems.

Or pressure, ofcourse.:ok:

Not on the co-pilot's side of a Caravan, or CT4....:E:ok:

TAS/10 + 7 is accurate enough, and that's not very hard.

IMHO to preference the T&B over an AH in IMC would be madness.

Anyway, the concept is to scan all the instruments and process all the information.

So now you're sitting there as a VFR Pilot who has inadvertently entered IMC thinking "S**t, S**t, S**t, I need to get out of here, umm, ok, turn onto reciprocal heading ummm...TAS is ummm... I'm going 120kts i'm at 2500ft so take that, divide by 1000, 2.5, times that by 2 ...no wait, 4, no 5 that's right, damn, haven't done this in a while... ok so that is 12.5 add that to 120 so about 132, now divide that by 10...umm... 13 add 7, 20 degrees, ok, damn, there is no 20 degree marking on my AH, just 15, 30, 45, ok, so just 15 plus a little extra I guess...sure, that looks about right...ok, now time it for the next minute..." Theres an extra 30 seconds worth of IMC you now have to turn back around and get out of so an extra minute assuming you were pretty accurate in your working out and got your heading correct and aren't heading out further into muck, that's a fair whack of your 178seconds CASA reckons you have left to live!

Or, I could go ""S**t, S**t, S**t, I need to get out of here, umm, ok, rate one turn, ok, now time it for the next minute..."

Now you tell me which of those 2 scenarios looks easier? Once again remembering that you're in IMC in a VFR Aircraft relying on an AH you don't really spend a lot of time paying attention to assuming that it's working correctly and isn't slowly toppling sending you into a spiral dive or isn't a bit lazy meaning you roll out at say 160degrees instead of 180, and yes you have you're DG and you can compare to that but once again you'd need to correct it because if it's like most DGs out there it's probably gone out by a reasonable amount during the turn and if you're in IMC you're stupid little Mag Compass is now bouncing around making it harder to get an accurate reading to reset your DG....

That T+B, if it's working, it's working, end of story. Getting out of IMC in a VFR Aircraft that'd be what I would teach someone to do and it's what I was taught to do as well, the AH becomes your backup to confirm, not the other way around. Plus teaching a VFR Pilot they'll be better off using the AH could lead them to a false thought of "Well, I'm already in it and I can use this AH so I'll just continue on" instead of "Nope, never really been advised to use AH before, not comfortable with that, I'll just got with the T+B to turn around and get the hell out!"

Yeah, I know, I'm looking at worst case scenarios but I'd rather assume the worst and be pleasantly surprised than the other way around!

caravan and Ct4 have co pilots ??????


Not on the co-pilot's side of a Caravan, or CT4....http://images.ibsrv.net/ibsrv/res/sr...ilies/evil.gifhttp://images.ibsrv.net/ibsrv/res/sr...ies/thumbs.gif

But any aircraft can turn at rates other than Rate 1 and still safely do a 180! ;)

During our RAF jet training we used to have to practice limited panel instrument recoveries from UPs, using the T&S after the AH had been toppled, as it is likely to do if you got the aircraft totally out of kilter, for example during aerobatics, or instrument failure and (very) slow scan....

The limitation of the instrument was that if you were pulling 'G' it greatly over-read. So you had to unload to 1G before using it. The advantage was that as it worked using a caged gyro it couldn't be totally toppled.

Speed (control),
G, (unload to 1 on the G meter)
Roll (opposite direction until the turn needle comes off the stop, then smartly centralise the ailerons),
Pull (stop the altimeter unwinding),
Repeat as necessary... Still rings a bell.

Ixixly

If you could advise how to accurately get attitude from a T&B ....

IMO, in your scenarios' relying solely on a T&B would mean that you wont use much of your "178 seconds that CASA reckons you have to live"

Really, using an AH is not as complicated as you are making it out be.

That would suggest the instructor who was responsible for the student pilot's ab-initio training, needs to be retrained himself; since understanding the use of the artificial horizon as an aid to both visual and IMC flight should be part of straight and level flight, climbing and descending.

I capitulate, I am grasping at straws there and pulling crap outta my arse!! You guys are correct that the AH is of course a better instrument in IMC conditions in an IFR Aircraft and possibly in a VFR Aircraft assuming the Pilots do keep an eye on them on a day to day basis and recognise when they are not performing well enough to be relied upon. But honestly I'd still rather use the T+B to get myself into a nice rate one to get back to VMC rather than the AH and use the AH as a backup to check I'm not climbing or descending, I shouldn't advocate it's sole use in such a situation this would be ignoring a perfectly valid source of information as Square Bear pointed out.

I should point out that was my point Square Bear, if you only have 178 seconds to live then you don't want to be using anymore of that than you have to.