Originally Posted by
SASless
HC,
If one sets the RadAlt but to 150/100/50 feet....pick your choice....does the helicopter know the difference between CAT 1, 2, 3 etc?
I should think that fancy 225 Autopilot you slavishly praise to us constantly would quite happily drive the machine to whatever height you selected.....would it not?
Would it not hold the Airspeed you select as well?
We know it would magically track the localizer to a gnats reared as well.
The 225 ILS system is quite capable of delivering the heli to 80' at 30 kts IAS, from which it can be beeped down to 30'. However the rules don't allow it to be used below the system minimum of 200'. To get down to 150' would be CAT 2, requires an operational approval from CAA and recurrent training every 6 months. And not even sure that Aberdeen is approved for CAT 2? Certainly other minor airports aren't.
So (and this directed to HF as well) it is not just about what tricks the heli can perform, it is what is allowed under the operational regulations and what has been certified. To certify such a system would have to take account of failure modes - ie if the heli was entering an auto-hover over the runway in IMC what would the pilots do if it stopped working - how would they even know if it stopped working until there was a crunch. So in all probability it is less about the money for certification, and more about whether such use is certifiable at all.
When flying an ILS in the 225, for Bristow it is SOP to leave the ILS coupled at DA if visual. The ILS system then takes the heli down to level flight at 80' on the localiser and the pilot beeps the speed well down. The aircraft handles this perfectly every time, and it eases workload in the sometimes tricky transition to visual flight with substantial speed reduction. BUT this can only be done if the pilots have the required visual references at and below DA. Thus they can monitor against visual references and take manual control if necessary (though it never is!).