PILOT WORKLOAD
A slow landing differs from a conventional landing in that ground roll is greatly reduced however important piloting problems remain so long as the aircraft cannot hover. During the approach to a slow landing, the following constraints apply:
(a) A minimum speed set by limits of lift or control.
(b) A maximum speed set by stopping ability and the strip remaining at touchdown.
(c) The approach path angle must be within narrow limits.
(d) The track over the ground must be accurately aligned with the strip in the final stages or the aircraft will leave the side of the strip shortly after touchdown.
(d) In order to avoid an undershoot or an overrun, very little height variation is allowable as the strip is reached.
Considerable pilot effort and skill can be necessary to fly within these constraints. This workload increases rapidly as the landing strip dimensions are reduced towards those needed by the aircraft when it is flown perfectly.
We all know that an inability to stop, whether on foot or in any vehicle, brings with it a fundamental need to plan ahead. In the case of an aircraft, any minimum flying speed limit requires the provision of overshoot and diversion procedures, together with the fuel reserves to carry them out. These procedures bring air traffic control problems and lead to repositioning sorties and logistic complications.
Because of these issues, pressure on the pilot is further increased at the very time that he is expected to perform at peak skill levels leading to the possibility of reduced accuracy and increased risk of failure. Even worse, the pilot may continue towards an inevitable accident because, under this pressure, he subconsciously rejects all options other than the approach in progress, despite the fact that the approach is beyond his capabilities or those of his aircraft.
Given a hover capability, these demanding requirements do not apply and the pilot just needs to establish a hover with the landing spot in view. This fundamental change reduces his workload for several reasons:
(a) The approach speed can be varied to suit external factors such as poor visibility or the need to fit in with other aircraft in the air or on the ground.
(b) Any descent path angle can be used so long as it is above local obstacles.
(c) The direction of the approach is not linked to the landing.
(d) Aircraft height at the end of the approach needs only to be above any obstacles and below any cloud.
(e) Because it is easy to adjust position over the surface once in the hover, acceptable position limits for the end of the approach can be measured in hundreds of metres to the left, right, forwards or backwards.
It is important to note that any trial results aimed at comparing pilot workload during different types of landing will only be valid if the landing sites chosen are equally limiting. Vertical landings on the small aft platform of a ship or in an urban car park may only be properly compared with slow or conventional landings made on a strip with a bomb crater or other genuine limit at each end. It is misleading to rely on measured short landing data obtained on a runway that is much wider and longer than aircraft performance alone would dictate. As discussed later, peacetime flying from an oversize runway is also inadequate training for any wartime restricted strip case.