Europe mulls new rules for aircraft with HUD and EVS

 - May 4, 2007, 10:49 AM

New regulations being developed by Europe’s Joint Aviation Authorities (JAA) may soon enable operators of HUD-equipped aircraft to hand-fly Cat II and Cat IIIA precision approaches and conduct Cat I approaches with a reduced runway visual range (RVR) of 400 meters instead of 550.

The proposed rules would also permit approaches in Cat II weather minimums to a decision height of 100 feet and an RVR of 400 meters on runways without touch-down zone and center line lights, as long as flight-crew training and all other Cat II requirements were satisfied. The same credits would be extended to airplanes with autoland systems. For operations of less than 400 meters, at least runway centerline lights are required.

The regulations now under consideration cover training and equipment/airframe qualification requirements directly related to what the JAA has elected to term “head-up display landing system” (HUDLS), to avoid the use of proprietary abbreviations. They are detailed in a notice of proposed amendment, NPA-OPS 41. The wording of the NPA has not been finalized, but a draft of the associated guidance material indicates the main elements of the proposal and the thinking behind it.

Cat IIIA for Turboprops
One result of the changes, which could take effect as early as next year subject to European Commission and JAA Committee approval, would be to make Cat IIIA operations possible for aircraft such as turboprops that do not have autoland systems.

The introduction of enhanced vision systems (EVS) is another issue addressed in the NPA. Seven members of the JAA’s all-weather operations steering group flew night approaches using an EVS in various low-visibility conditions and at night in mountainous terrain. They found the system provided additional situational awareness during taxiing at night, in low visibility and during approaches in VMC at night. It also provided benefit in earlier acquisition of the visual references during instrument approaches under many, but not all, circumstances.

They concluded that the variation in system performance in differing atmospheric conditions called for a rule that broadly covered the average performance but was constructed to be self-limiting. Moreover, a HUD is considered to be an essential element of an EVS for which some form of operational credit is sought.

The JAA agrees with the FAA that if an allowance is granted to use enhanced visual references instead of the natural view of the visual references, a natural view of the visual references should still be required before landing. The proposed rule, accordingly, would allow a pilot to continue an approach beyond a normal 200-foot decision height using an EVS view of the visual references but require a natural view of those references by 100 feet.

In fact, the visual reference requirements have been taken directly from FAR 91.175. RVR limits were selected to give some benefit in the majority of situations, rather than trying to accommodate the best-case scenarios. Overall, the proposed rule is closely harmonized to the FAA rule but includes some additional criteria regarded as necessary in the European environment until greater operational experience is developed.

Enhancing Safety
The main objective of the NPA is to enhance safety in approach and landing operations, particularly in conditions of reduced or low visibility. It also recognizes that for turboprop airplanes, HUDLS is the only commercially viable way of achieving Category III approvals. At the same time, allowing reduced minimums will make it easier for operators to develop a business case for the HUD equipment.

A trial involving around 140 simulated landings satisfied the JAA that the improved guidance provided by a HUDLS compensates fully for the reduction in RVR for Cat I operations and the absence of touch-down zone and center line lights for Cat II operations. In the case of autoland systems, the compensation comes from the reduced workload and improved precision they deliver.

NPA-OPS 41 replaced a previous proposal, NPA-OPS 20, which introduced stabilized approach requirements, the continuous descent final approach (CDFA) concept and a new set of airport operating minimums, all based on work to harmonize the all-weather operations issues with FAA. The JAA considers the introduction of these concepts into JAR-OPS 1 to be important from both a safety and a commercial perspective. The 290 comments received in response to NPA-OPS 20 resulted in such a large change that it was abandoned and the new proposal developed.

The stabilized approach requirements are in line with the approach and landing accident reduction and controlled flight into terrain programs promoted by the International Civil Aviation Organization and the Flight Safety Foundation. The use of stabilized approach criteria on a continuous descent with a predetermined vertical path facilitating a continued awareness of vertical position relative to the required profile is seen as a major improvement in safety during the conduct of such approaches.

The objective of the proposed EVS rule is to allow a benefit in instrument approach operations to be gained by the voluntary installation of EVS equipment without affecting the safety of the operation.

Specific training of flight crews will be required for all the new types of operations included in the NPA, and operators will be required to develop new procedures if they do not already voluntarily comply. Many operators already apply the CDFA techniques, however.

Economic Benefits

The JAA notes that development of a common standard for airport operating minimums will ensure that competition between U.S. and European operators is based on equal and fair terms, as far as all-weather operations are concerned. In addition, the development of common minimums will facilitate a more cost-effective production of operations manuals.

There are wider economic benefits. Operators will be able to continue operations in lower visibilities and so reduce diversion rates. Manufacturers will be able to make returns on the research-and-development costs of the new equipment. And by encouraging competition, innovation and investment, the new regulation will improve choice of all-weather operations equipment.

Initially there may be a cost implication to implementing the changes of minimums, crew procedures and training. This should be a one-off cost and is believed to be acceptable, considering the overall safety and economic benefits. It is also avoidable since operators can continue with the higher minimums if they prefer.

These rules proposed under NPA-OPS 41 are in the final development stage, but have a way to go before they are adopted.

The next phase is for the European on (EC) to consider NPA-OPS 41 in December for incorporation into the new EU-OPS 1. EU-OPS 1 is already law for the European Union’s 27 member states (plus Switzerland, Norway and Iceland), but becomes applicable only after mid-2008 following the current transition period. If the EC agrees to this proposal, the NPA will then go before the JAAC for adoption and incorporation into JAR-OPS 1 early next year. JAR-OPS 1 continues to be applicable to non-EU JAA member states. This allows EU-OPS 1 and JAR-OPS 1 to remain synchronized.