Today is the day that FAR 135.160 goes into effect. This requires a radar altimeter (“radio altimeter” in the FAA’s parlance or “radalt”) for most U.S. helicopters. The device will display the number of feet the aircraft is above the ground. Every airliner that was ever crashed into a mountain had one of these. What stopped the crashes was the terrain awareness and warning system (TAWS).
Radalt was useful in the old days because it could ring a bell for the pilots when the aircraft was, e.g., 200′ above the ground on an instrument landing system approach. If neither the runway lights nor approach lights were in sight at that point it was time to add power and fly back up into the air (“missed approach”).
Even in 2014 when this rule went into effect it was unclear why it would be a good idea to stuff a radalt (cost range: $17,000 to $100,000 depending on aircraft and whether installed new or retrofitted) into a helicopter rather than GPS+database TAWS system that can say “There is a big radio tower ahead!” or “Climb because you are about to crash into the ground.”
The new rule applies even to helicopter operations that are limited to visual flight. The chance that the pilot is looking down at the instrument panel is small (10-20 percent) because the aircraft is being controlled by reference to the natural horizon. Combine that with the chance that the pilot would be looking at the radalt number and I would say that there is a near-zero chance that a pilot in a dangerous situation would ever become aware of the radalt value.
The measured GDP may not have declined too much as a result of this rule, but we’ll have spent a bit slice of it on something that has no value and may actually reduce safety (the extra weight of the radalt reduces the safety margin of reserve power for maneuvering out of bad situations).
[Note that a kind of successor and cousin to TAWS is the flight simulator view of the world presented to pilots in a synthetic vision system. This has been standard on cheap airplanes (home-builts, four-seaters, etc.) since 2010 and maybe it will be common on commercial airliners by the year 2025 or 2030 (see this Aviation Week article from 2015). I wrote about this in 2005 with the subhead “How a 10-Year-Old Will Outfly You in 2010”]
When all of this is done, of course, the typical $10 million Sikorsky or Airbus helicopter will still have less collision-avoidance capability than an $800 drone from DJI.
- the FAA’s 2014 rule, in which they estimated $311 million in total costs for a range of changes, with $21 million devoted to radalts