365 n auto pilot

[weedwacker]

Hi there was wondering if there is any one out there that can help with info or experience with a 365n with a sperry auto pilot system in it PLEASE?

[Geoff Williams]

WW

The 356N has an American STC for the installation of the Sperry 7000 auto pilot. This is a common type of AP for the period, fitted to types like S76, BK117 and others, and the functions are as per other 7000 installations.

The STC number for the 365N is SH2215NM and the RFM supplement is 27-5130-11. Hopes that's of some help.

Geoff

[weedwacker]

Thanks heaps Geoff will look in to that.

Was wondering if you had any experience with other a/c with the same system of auto pilot ie: Alt hold function dropping out & Yaw hunting in fwd flt? :confused:

[Shawn Coyle]

What were the conditions when the altitude hold dropped out? Any other symptoms / warning lights / indications?

[Geoff Williams]

WW

Only seen/flown one example of the 365N Sperry. It's data transducers are slighlty different from other 7000 installations, for example the S76B. The ALT PRE and baro info is supplied from the altimeter and not a separate ADC unit. The altimeter has an encoding function which supplies the AP computer with the signals to drive the altitiude functions. Dropping the ALT could be many things including the engaging of another pitch function, or the disconnection of the CPL'r, to an AP computer malfunction.

Shawn is quite correct, more observations are required to make a guess as to the cause of the de-coupling.

As for the yaw, there are rate gyros and other associated yaw components mounted under the floor that can cause weird yaw effects. Best trick, find a good E&I greenie who knows the type of AP.

If it's the one in QLD then that's the one I've flown when it first arrived in country for HR. Their greenie is good on the unit so might pay to give him a ring.

Geoff

[weedwacker]

Hay Geoff
The heli info it loses vertical modes after 30min in flt genraly. Also in the hover the auto pilot does not hold heading with changes of collective settings, seems to work in cruse.

[HR GREENIE]

ww

The way the Pre alt works is when you set the desired hight the AP will use the grey code from the Altimeter till you get to aprox 50 ft of the set hight then it will switch across to the ADC in the nose this will be shown on the mode selector by switching from pre alt to cap were the signal from the ADC is used to control hight. the most likely cause of the system dropping out is a faulty ADC .
Collective issues may be due to miss alignment of the collective transducer.
Heading hold in hover maybe a u/s air speed switch.

HR GREENIE

[Shawn Coyle]

Many things will depend on how the system is supposed to work. And the problem is that manuals that describe the system are not well written, and knowledge thereby becomes lacking. Many of these systems will not hold heading in the hover, as the yaw channel is very slow to react. Once in forward flight, heading hold should be done through the roll channel, and the yaw channel relegated to turn coordination. But you have to know the system intimately to be able to tell this.