There is news in every direction these days, but I still follow the press conferences by the National Traffic Safety Board (NTSB) concerning the midair collision over the Potomac River one week ago.
As I shared with my first post on this topic, I try to avoid speculation about aircraft accidents until all the facts are known. Having flown for 50 years, I know there are always a number of factors that go into any accident.
Yesterday, the NTSB shared important information, and I do think they are narrowing the focus in a search to determine what happened.
It seems clear that the commercial regional jet accepted a change in their approach to land on runway 33 at Reagan National and was carrying out that maneuver when the collision occurred. It is also clear that since the collision occurred at about 300 feet, the Black Hawk military helicopter was above an altitude restriction of 200 feet. Flight tracking also suggests the helicopter diverted from the standard flight path.
The question remains: why?
Here are the areas of inquiry that most interest me.
The tower controller:
- he can be heard on at least two occasions, telling the pilot of the Black Hawk helicopter that they have traffic and both times the helicopter pilot stated they had the traffic in sight….we should find out what the tower controller saw on his screen with regard to the helicopter’s altitude. It should not have been above 200 feet.
- because the controller was told the traffic was in sight by the helicopter, the controller did not provide any reference information about where the traffic was in relationship to the helicopter nor did he provide a heading that would have kept the helicopter away from the aircraft…not so much an error as a very unfortunate omission.
- the helicopter pilot requested a “visual separation clearance,” and the controller responded, “vis sep approved.” What did the controller mean exactly (more below)?
The Black Hawk Pilot:
- traffic was pointed out twice to the helicopter and twice the pilot reported “traffic in sight.” It is highly doubtful in my view that the helicopter actually saw the traffic the controller cautioned about….pilots just don’t hit things they see.
- the helicopter pilot, upon receiving the second caution for traffic, said they had it in sight and requested a “visual separation clearance.” What did he actually mean by that (more below)?
- and, most importantly, why would the helicopter have been high and slightly off the designated course for the route they were flying, even making a slight turn to the right apparently before the crash which was away from their flight path?
The Helicopter’s Altimeter
- these devices are very accurate provided the correct barometric pressure is set manually into the altimeter. NTSB will closely examine this and all instruments aboard the helicopter, but even a small error in a setting could cause a 100 foot deviation where the indicated altitude was different than the actual altitude. Had the altimeter setting been updated on a very cold (20 degree) night is something we should know. In listening to the voice recording, the tower controller was informing landing aircraft of the proper altimeter setting and it was changing.
About “pilot/controller speak:”
One of the important aspects of our air traffic management system is the language used by controllers and pilots is carefully constructed and common across the entire system.
In over 5,000 hours of flying, I have many times been instructed by a controller to “maintain visual separation” from another aircraft. This instruction is issued when a pilot sees the other aircraft and it specifically requires the pilot to “maneuver” in a manner to avoid the other aircraft.
Now, I did not fly helicopters, but in all of my flying I never requested a “visual separation clearance.” Interestingly, the tower controller “granted” the request, instructing the helicopter to pass behind the traffic.
At that moment, the collision was seconds away.
Hopefully the cockpit voice recorders will reveal exactly what the helicopter pilots elected to do with their “clearance.” The flight records suggest they turned slightly right and climbed above 200 feet. The question remains, why? Did they believe the 200 foot restriction was lifted? Did the altimeter show an altitude of 200 feet when it was actually 300 feet? Did they turn to stay behind an aircraft other than the one that the controller cautioned them about?
While the focused has narrowed, the questions remain. However, it seems we are getting closer to learning why.