Why must I have a slip and turn indicator?
 

I'm currently studying up for my CPI. Today we were discussing the minimum equipment requirements as per CAO 20.18.

Appendix 1 tells me in need an air speed indicator, altimeter, compass and as accurate time piece for PPL flights. If it is charter flight I need to add a turn and slip indicator and outside air temperate indicator.

Can any one tell why I need a slip and turn indicator? All the other items make a lot of sense to ensure a safe flight but I can't see why the logic behind the slip an turn.

Just in case you are turning or slipping & don't know about it :ok:

So when you inadvertantly enter cloud you will be able to do a coordinated 1 (or 2) minute turn back to where you came from.

Typically in an *old school* configuration, eg 90% of Cessna's, T&B / T&S indicators are powered electrically to go with the vacuum powered AH & DG to give you a level of redundancy in the event of an engine or vacuum pump failure. A *good* pilot could happily fly through cloud on the T&B in the event of an AH failure.

As XXX said, redundancy is why. Private Flight if you decide to not have one or fly with it Inop then that's your prerogative and you're life that gets put at additional risk if something should go horribly wrong, but in a commercial environment it would be considered unacceptable to not have such a simple and basic piece of equipment not installed and working, admittedly though they are a lot more expensive than I had imagined!!

"Happily?" I realise you have inverted commas the good bit to make your point, but believe me it wouldn't matter how good you were. Any pilot would be in dead serious trouble if he lost the AH and had to fall back on the Turn Coordinator or the Turn and bank indicator. Unless of course he was current in the last few weeks on limited panel flying in IMC both in a real aircraft or synthetic trainer. Readers may recall from about ten years ago, a Mooney (?) flying near Mildura (?) at night lost his AH and decided to turn back towards Mildura and land. With only a Turn and Bank indicator he didn't last long and crashed after coming apart out of control.

Reminded me of a quiet event when a 150 hour student with his own Cirrus was practicing instrument flying in a synthetic trainer called, I think, an Elite flight trainer. The student was happily doing several practice holding patterns. The suggestion was made that it might be worthwhile practicing flying without an AH in case one night the AH fell over. The student said it would never happen in his EFIS Cirrus so no need to make it hard for himself.

After about the fifth holding pattern with the student congratulating himself how good he could fly on instruments, someone passing by the Elite trainer, quietly failed the AH. It took less than one minute before the student was in a screaming spiral dive cursing the poor old Elite trainer. Nothing wrong with the synthetic trainer apart from the failed AH. The problem was the cocky pilot. Even after that rather dramatic ending he still refused to practice limited panel on instruments. Last I heard of him was that he was a flying instructor teaching instrument flying...:rolleyes:

So I thought the requirement could be in case of inadvertently entering IMC. But as Centaurus says if that happens I'd really want a AH rather than a S&TI. Its interesting that AH is not required as part of the minimum equipment requirement.

Caught up with an old instructor of mine recently and he was telling me that he braved IMC on an electric T&B for over 30 mins. He had get-there-itis but the added bonus of definitively knowing he wasn't going to hit anything. Braver than I. Certainly a good skill to practice if you are bored on a cross country flight one day.

Nah, has got the skills to pull it off safely, just probably shouldn't have done it.

There's plenty of pilots out there that have done it with no instruments other than ASI, ALT and perhaps a VSI. One of those pilots I know lost the roof off his aircraft whilst doing it :uhoh: so not always a happy ending :ok:

If you think it would never happen to you, then how about this. En-route Townsville to Darwin in a Lincoln bomber in the 1950's, the AH toppled terminally leaving the pilot flying at night with primary panel only - meaning the Turn and Bank indicator. This happened at the half-way point with three hours to go. Due seasonal weather aircraft in cloud most of the way but when not in cloud was black night IMC. The aircraft arrived over Darwin about one hour before dawn. Rather than risk an instrument let down on the Turn and Bank indicator, the pilot elected to fly within a 20 mile radius of the airport until as the sun came up he could see holes in the cloud. He then let down through the holes until visual with the ground and airport.

Another thing to remember about a failed AH is that it may fail slowly (not too sure about EFIS AHs in lighties) and may not be picked up until you are already in a spiral. Also have something to cover up a failed AH because seeing it sitting on some weird angle or spinning around is a rather large distraction while flying limited panel.

A basic AH is vacuum powered, and therefore has no prominent failure flag. The "failed suction pump" indication is likely to be well outside the primary scan area.

That's one reason why why the law requires, at minimum, some sort of turn indicator. Being electrically powered, the failure indicator is more prominent.

Why do you need a T & B simple really if all else fails it can save you and your passengers lives.


No more complicated than that !!!!!!!


Practice flying limited panel T & B, ASI, Altimeter and ROC it is very rewarding to get it right and the blue is on top and the aircraft stays straight and level.

Isn't the T & B properly called a Turn and Balance rather than Turn and Bank?

Was a time when flight in IMC was being undertaken without the benefit of attitude indicators. Charles Lindberghs Spirit of St. Louis contained nothing but fuel pressure, oil pressure and temperature gauges, a clock, altimeter, tachometer, airspeed indicator, bank and turn indicator, and liquid magnetic compass.

Kingsford-Smiths Southern Cross also had a similar level of basic instrumentation.

'uncle8' It's mostly known or called a Turn & Bank indicator by the Yanks but I believe it's a Turn & Balance indicator meaning if the ball is centered & the bat (if it's a ball & bat unit) is lined up with the offset ref mark then yr turning correctly/balanced at a rate one turn.
At the end of the day they mean one of the same thing when the term 'T&B' has been written.
Used to reg use the T&B on many an IFR renewal.

Wmk2

The CAO refers to a Slip and Turn Indicator. It would seem "Slip" and "Balance" are interchangable.

Thanks for all the posts so far.

If I can summarise, the additional requirements for Charter operation is in case of inadvertent IF. The regs specify a S&T rather than AH because either:
> Thats all Kingford-Smith had so it should be good enough for the rest of us or
> Electrically power instruments are more reliable than vacuum indicators (that is why T&B rather than AH)

Is that a fair summary?

By the way I'm not sure what a ROC is. Rate of Change indicator? Is this same as a VSI?

Back in 1960 when I was a RAAF Apprentice Instrument Fitter ROC was Rate of Climb and post the WW II the rate gyro was always referred to as a Turn and Bank.


What would the RAAF know ?????

You may also find the rules allow for a second AH (electrically drive if the primary is vacuum driven) so long as there is a balance ball incorporated somewhere, in lieu of the T&S. It might also need a greater degree of pitch freedom than the primary as well (all this based on an un-researched memory of NZ rules).

The RAAF lost all credibility in my mind when they couldn't land their 737 at Lorde Howe (and returned home) and Virgin? landed shortly after.

Not quite. You can be legitimate IFR and lose your AH. You can be inadvertent IMC but use your AH.