Thread on cause of #KobeBryant crash.
1/ I've flown commercially in the crash area for many years. When the crash occurred, I tweeted a first impression, that the crash bore the hallmarks of something called a CFIT event.
1/ I've flown commercially in the crash area for many years. When the crash occurred, I tweeted a first impression, that the crash bore the hallmarks of something called a CFIT event.
2/ Controlled Flight Into Terrain is when a properly functioning aircraft is flown, under control, into the ground. Not uncommon when someone suddenly enters clouds.
3/ If they're not expecting to transition from piloting using visual ground reference to their instruments, it's easy to become disoriented.
4/ The reason I thought this was CFIT was the photo of the crash site, which showed two things: 
5/ First, the helo was moving fast, evidenced by the extent of its disintegration. And second, that it was developing power, because the brush appeared to have been chopped down in a circular fashion...
6/ ... which is consistent with the rotors exerting a lot of force. Though I didn’t know at the time what the weather conditions were, I suspected a deck of clouds contributed to this tragic crash. This was borne out.
7/ Though there’s no way to be completely sure of this analysis, I’d be willing to bet a large sum that this is how it unfolded and what the accident report, when it comes in a year or so, will look like:
8/ The pilot of the chopper had departed from John Wayne Airport, to the southeast, and flew northbound into the Los Angeles area. He flew over the hills that separate west LA from the San Fernando Valley and arrived southeast of Burbank Airport.
9/ There, the weather had crapped out, though not too badly. The closest airport to the crash was reporting an 1100-foot overcast and 2.5 miles of visibility. Totally manageable for a properly equipped and rated pilot. He could have landed easily. Instead, he held for 15 minutes.
10/ That can make a pilot antsy – for some, carrying VIP passengers, even more so. The conditions were something called IFR – Instrument Flight Rules.
11/ To fly in IFR conditions – low or no visibility, like in the clouds – you usually have to have a type of clearance from air traffic control (ATC) called an IFR clearance. Then, instead of being able to navigate by looking outside, you rely on instruments to fly.
12/ The chopper asked for something called a Special VFR clearance. That’s a way to operate near an airport when the weather is low, but not too low. It allows you to fly as close to clouds as you want, just not *in* them. Without a Special, you have to maintain greater distance.
13/ You can get a Special VFR clearance when there’s a mile of visibility, and, over the cloud deck, there was. The pilot said so, reporting on the radio that he was in visual, or VFR (Visual Flight Rules) conditions.
14/ ATC granted the Special VFR clearance with instructions for the pilot to transition through the area by flying north of both Burbank and Van Nuys airports by following Interstate 5 to Highway 118. That would keep him out of the way of airplanes taking off from Van Nuys.
15/ ATC’s instructions were to maintain Special VFR conditions – clear of clouds – at or below 2500 feet. He wasn’t allowed to climb higher than 2500 feet, but he was allowed to fly at any altitude up to that. So far, so good, and on his way he flew.
16/ The pilot wanted to follow Highway 101 westbound to his destination, Camarillo, which was due west. Pilots often fly by reference to roads. To get to the 101, he requested a turn to the south once he was clear of Van Nuys airport.
17/ It is now moments until the crash, and after the pilot flew north of the airports and turned south, things started to go wrong. He increased his altitude from 1300 feet to 1700 feet. This *could* have been (no way to know) because the cloud deck was thickening below him.
18/ This detail could be relevant, though it might not be: He reported his altitude as 1500 feet, but his aircraft was telling ATC he was at 1700 feet. That *could* be a sign of getting behind the curve in the cockpit, perhaps as conditions worsened.
19/ It signaled some uncertainty. And then his altitude readout on the radar shows a touch of erratic behavior in the way he changed altitude, descending again to 1300 feet and then back to 1400 feet. This heralded the final, and lethal phase of this flight.
20/ At this point in the ATC transmissions, the pilot is no longer heard. Either he wasn’t transmitting or the controller wasn’t hearing him. It’s not clear. Either way, his voice is not on the recording and we can’t tell if the controller was still receiving him.
21/ Remember that the danger here is reduced visibility. A cloud deck blanketed the mountains ahead and the reduced visibility made it unlikely he could see them until they were close. And, it can be hard to tell how much a cloud deck is sloping. It can be confusing.
22/ Avoiding that confusion is the reason you fly on instruments, not visually, in instrument conditions. But this pilot was flying visually. He was expecting to see the 101, and if he could, he would simply turn and follow it. That would have been fine.
23/ But then, at the very end of the flight, the pilot appears to have seen, suddenly, that he was about to fly into the mountains. His radar readout shows a drastic attempt to gain altitude, hauling the chopper up to 2100 feet – the final readout before radar contact was lost.
24/ The helicopter flew into the mountain. It was near Las Virgenes Road and Willow Glen Street, near Calabasas.
25/ If this proves to be the cause of the accident, it is a repeat of many before it. This might sound obvious, but a pilot has to know where the ground is. That can be challenging in an area where the terrain rises rapidly, and especially in bad weather.
26/ In the Special VFR clearance the pilot received he had been allowed to climb to 2500 feet. He never took advantage of that altitude, choosing instead to go lower. This is probably because he reasoned that it was high enough to safely intercept the 101.
27/ And it should have been. The hills there are only go to about 1200 feet high. Not that you want to choose an altitude so close to them if you can’t see them, but his choice of altitude might not alone have been enough to lead to the crash.
28/ So, my initial assumption that this was a controlled flight into terrain might be wrong. It seems more likely that the pilot became disoriented to some degree when things started looking bad. Either he never saw the 101 so he could navigate along it, or he lost sight of it.
29/ Conditions were marginal, he was flying quickly – roughly 150 miles per hour – and things were happening quickly. Whether he saw the 101 at some point or not, he overflew it. That might have made him panic in the way he did to try to climb as rapidly as he did.
30/ And doing that could have led to a loss of control of the helicopter. The accident investigators will eventually come up with a hypothesis when they analyze the wreckage and the site.
31/ But, in sum, all signs point to a straightforward case of pilot error. Most of the hundreds of small aircraft accidents every year are.
32/ Had he realized sooner that he would be in trouble he could have flown higher than he was cleared. At worst he would have had to explain why.
33/ Most aviation accidents could have been avoided. This one certainly could have been. He could have landed at Van Nuys. He could have gone a longer way around the weather. He could have told his passengers he was sorry, but they’d have to wait.
34/ Had he filed an IFR flight plan, he would have been at controlled altitudes guaranteeing a safe distance from the ground.
35/ Every beginning pilot hears about something called get-home-itis, a desire to get someplace, for whatever reason, that overrules judgement and lures pilots into making deadly mistakes. This will prove to be some variation on that old theme.
36/ RIP Gianna Bryant, Kobe and everyone else on the flight.
A tragic waste.
A tragic waste.
