Recommendation Date
Recipient Name
ATD MoT
Text
Align the requirement for the fitting of Ground Proximity Warning Systems (GPWS) with the ICAO recommendation on this topic.
Reply Text
Amendment 13 of 13.4.79 to ICAO 6 introduced a standard which required all turbine engine aeroplanes with a take-off weight in excess of 15,000 kg or authorised to carry more than 30 passengers to be equipped with a Ground Proximity Warning System. The standard is applicable to aeroplanes for which the individual C of A was first issued on or after 1.7.79. The amendment also recommended the requirement be applied regardless of the issue date of the individual C of A.
The recommendation was adopted by New Zealand in 1984 by AD/GEN/13 with an effective date of 31.12.85, after it was generally accepted the early problems with false warnings had been largely overcome. After representations by Safe Air on cost benefit grounds for the Argosy aircraft the AD allowed concessions to be permitted for existing aircraft "used entirely or mainly for freight operations within New Zealand".
Subsequently it was amended as AD/GEN/13A on 1.8.86 changing the applicability to turbo jet aircraft, thus excluding turbo prop aircraft, because of the problems of nuisance warnings. (The fact that GPWS is not very effective for turbo prop aircraft, due to their lower speeds requiring a larger closure gradient to activate a GPWS warning, this was pointed out at the time of the original AD). In the US, GPWS requirements were applied to all large aircraft operating under Part 121, but only to large turbo jet aircraft when operating under Para 135, as in New Zealand.
However, in April 1990 the FAA issued an NPRM proposing to extend the requirement to all large turbine powered aircraft operating under Part 135 because there had been quite a number of controlled flight into terrain accidents to turbo prop aircraft which could have been prevented had GPWS been fitted to the aircraft. It was also noted the cost of suitable equipment for smaller turbo propeller aircraft has fallen significantly in recent years. However, to date, no final ruling has been received on this proposal.
In the accident to ZK-FTB the MODE 3 Descent After Takeoff envelope would have been penetrated and a "Don't sink" warning due to an altitude loss of more than 10% below 700 ft AGL should have been given. Thus the accident may have been preventable if GPWS was fitted.
TAIC should be advised that ATD is awaiting the outcome of the FAA rule on this issue and will be reviewing the subject in general to determine if circumstances have changed at all since the revision of the AD.
The recommendation was adopted by New Zealand in 1984 by AD/GEN/13 with an effective date of 31.12.85, after it was generally accepted the early problems with false warnings had been largely overcome. After representations by Safe Air on cost benefit grounds for the Argosy aircraft the AD allowed concessions to be permitted for existing aircraft "used entirely or mainly for freight operations within New Zealand".
Subsequently it was amended as AD/GEN/13A on 1.8.86 changing the applicability to turbo jet aircraft, thus excluding turbo prop aircraft, because of the problems of nuisance warnings. (The fact that GPWS is not very effective for turbo prop aircraft, due to their lower speeds requiring a larger closure gradient to activate a GPWS warning, this was pointed out at the time of the original AD). In the US, GPWS requirements were applied to all large aircraft operating under Part 121, but only to large turbo jet aircraft when operating under Para 135, as in New Zealand.
However, in April 1990 the FAA issued an NPRM proposing to extend the requirement to all large turbine powered aircraft operating under Part 135 because there had been quite a number of controlled flight into terrain accidents to turbo prop aircraft which could have been prevented had GPWS been fitted to the aircraft. It was also noted the cost of suitable equipment for smaller turbo propeller aircraft has fallen significantly in recent years. However, to date, no final ruling has been received on this proposal.
In the accident to ZK-FTB the MODE 3 Descent After Takeoff envelope would have been penetrated and a "Don't sink" warning due to an altitude loss of more than 10% below 700 ft AGL should have been given. Thus the accident may have been preventable if GPWS was fitted.
TAIC should be advised that ATD is awaiting the outcome of the FAA rule on this issue and will be reviewing the subject in general to determine if circumstances have changed at all since the revision of the AD.
Related Investigation(s)