Page 403 - UK Air Operations Regulations (Consolidated) 201121

Part CAT - ANNEX IV - Commercial Air Transport Operations

(1) a unique tone should precede the voice message; a further tone after the voice may
enhance uniqueness and attract more attention without causing undue annoyance;
(2) the perceived tone and voice should be moderately urgent;
(3) the message should be compact as opposed to lengthy provided that the meaning is
not compromised, e.g. ‘One fifty feet’ as opposed to ‘One hundred and fifty feet’;
(4) an information message is preferable (e.g. ‘One hundred feet’); messages such as
‘Low height’ do not convey the correct impression during deliberate descents through
the datum height;
(5) command messages (e.g. ‘Pull up, pull up’) should not be used unless they relate
specifically to height monitoring (e.g. ‘Check height’); and
(6) the volume of the warning should be adequate and not variable below an acceptable
minimum value.
(d) Every effort should be made to prevent spurious warnings.
(e) The height at which the audio warning is triggered by the radio altimeter should be such as
to provide adequate warning for the pilot to take corrective action. It is envisaged that most
installations will adopt a height in the range of 100-160 ft. The datum should not be
adjustable in flight.
(f) The preset datum height should not be set in a way that it coincides with commonly used
instrument approach minima (i.e. 200 ft). Once triggered, the message should sound
within 0.5 sec.
(g) The voice warning should be triggered only whilst descending through the preset datum
height and be inhibited whilst ascending.
CAT.IDE.H.145 GM2 Radio altimeters
RADIO ALTIMETER DISPLAY
An analogue type display presentation may be, for example, a representation of a dial, ribbon or bar,
but not a display that provides numbers only. An analogue type display may be embedded into an
electronic flight instrument system (EFIS).
CAT.IDE.H.160 Airborne weather detecting equipment
Helicopters with an MOPSC of more than nine and operated under IFR or at night shall be equipped
with airborne weather detecting equipment when current weather reports indicate that thunderstorms
or other potentially hazardous weather conditions, regarded as detectable with airborne weather
detecting equipment, may be expected to exist along the route to be flown.
CAT.IDE.H.160 AMC1 Airborne weather detecting equipment
GENERAL
The airborne weather detecting equipment should be an airborne weather radar.
CAT.IDE.H.165 Additional equipment for operations in icing conditions at night
(a) Helicopters operated in expected or actual icing conditions at night shall be equipped with a
means to illuminate or detect the formation of ice.
(b) The means to illuminate the formation of ice shall not cause glare or reflection that would
handicap crew members in the performance of their duties.
CAT.IDE.H.170 Flight crew interphone system
Helicopters operated by more than one flight crew member shall be equipped with a flight crew
interphone system, including headsets and microphones for use by all flight crew members.
CAT.IDE.H.170 AMC1 Flight crew interphone system
TYPE OF FLIGHT CREW INTERPHONE
The flight crew interphone system should not be of a handheld type.
CAT.IDE.H.175 Crew member interphone system
Helicopters shall be equipped with a crew member interphone system when carrying a crew member
other than a flight crew member.
CAT.IDE.H.175 AMC1 Crew member interphone system
SPECIFICATIONS
The crew member interphone system should:
(a) operate independently of the public address system except for handsets, headsets,
microphones, selector switches and signalling devices;
(b) in the case of helicopters where at least one cabin crew member is required, be readily
accessible for use at required cabin crew stations close to each separate or pair of floor
level emergency exits;
(c) in the case of helicopters where at least one cabin crew member is required, have an
alerting system incorporating aural or visual signals for use by flight and cabin crew;
(d) have a means for the recipient of a call to determine whether it is a normal call or an
emergency call that uses one or a combination of the following:
(1) lights of different colours;
(2) codes defined by the operator (e.g. different number of rings for normal and
emergency calls); or
(3) any other indicating signal specified in the operations manual;
(e) provide a means of two-way communication between the flight crew compartment and
each crew member station; and
(f) be readily accessible for use from each required flight crew station in the flight crew
compartment.
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