HF brace yourself, long post coming up! The L2 and 92 autopilots are of similar capability in terms of precision and min IAS for use, although the 92 has more "bells and whistles" modes. The underlying technology is of error detection and correction, ie an error has to develop first, then the AP makes a correction.
The 225 is in a different league with the whole AP being driven by hybridised parameters of inertial data plus the parameter in question (eg inertial plus pressure altitude for ALT) with the emphasis on the inertial. This makes it incredibly precise in those inertia related modes (ALT, LOC, GS etc) and slightly less precise, but still very good in the likes of IAS - because gusts etc mean there isn't necessarily a direct correlation between IAS and inertial speed. Min IAS for a number of modes such as ALT, GA is zero, min for IAS is 30 kts. This allows the upper modes to be engaged until very late in eg a night offshore approach, down to 30kts IAS which might be very low ground speed.
As to the point about manual flying skills, it is a good one. Clearly one needs to have both manual skills and a good understanding of the behaviour of the automation. But how to set the balance?
The AP is so much better and more consistent at flying eg an instrument approach in bad weather, or a night takeoff, than the crews, that in my mind it would be criminal for the pilots to take the less safe option of flying these manually and reducing the safety of the flight with passengers, just for their own practice. That is why the Bristow OM requires use of automation in such conditions. Manual practice is only allowed in day VMC.
Does this degrade manual flying skills, well maybe BUT, for example when I learnt to fly on a Bell 47, to start with 99% of my attention was on maintaining the rrpm at 3050 to 3100 in the hover, using the throttle. Now I fly helicopters that don't have a throttle at all, so that skill is completely redundant.
Similarly, I fly a helicopter that, in its entire history with Bristow, has only had one event where a manual ILS had to be flown, and that was caused by a software bug now fixed. So just how much effort and increased risk to the passengers should go into maintaining superb ILS manual flying skills in bad weather? I would say that you just need to be able to struggle by, not put in a polished performance if the less than once in several lifetimes event occurs. There is just so much redundancy that its hard to imagine a situation where a coupled ILS couldn't be flown.
All that is fine for old codgers who can fly, what about those coming new into the industry. Clearly they do need to develop manual flying skills, but my view is that, whilst this can be done on the line in reasonable weather, anything more tricky must be done in the simulator, which we are fortunate enough to have on the doorstep. There is no rule that says pilots can only go into the Sim once every 6 months! I'm glad to see that after a bit of a hiatus, Bristow is once again providing copilot development sim trips in between the 6 monthly checks.
HC
Last edited by HeliComparator; 28th Aug 2013 at 08:49.