NW 188

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The story of Northwest Airlines trip 188 was featured for several weeks in the media after an incident on 21 October 2009. It’s the story of the Airbus A-320 enroute from SAN to MSP, which lost contact with controllers at ZDV and overflew MSP, at altitude, reaching EAU before reestablishing contact. There are lots of side stories about subsequently getting the airplane on the ground, what the pilots had been doing, FAA and other procedures, etc. Naturally, as the sole ATC expert many of my friends and acquaintances have, I get asked about it frequently.

First, I want to clarify that I retired in 1997, nearly four full years befor 9/11 happened. Some things have changed as a result of that tragedy, and consequently, some of my experiences are no longer relevant insofar as current rules and procedures are concerned. Nevertheless, they still may have relevance for the purpose of providing context and meaning to certain situations. With that in mind, let’s review the circumstances.

Quelle horreur! Nobody was talking to this airplane for hours. Isn’t that dangerous? Isn’t that unusual? My answer in both cases is “no.” Our ATP (Air Traffic Procedures, FAA Handbook 7110.65) has hundreds of words that relate to how to handle IFR flights who have lost communications with ATC. Moreover, every instrument student is drilled in lost comm procedures as a large part of their training, and such procedures are laid out in the Airman’s Information Manual (AIM). Not only are all parties singing from the same hymnal but they’re well rehearsed.

I had several experiences with Lost Comm flights in my career. I still remember my first—I was working a Cessna 310 at 70 (7,000 feet) northbound on V3 north of CHS. Thus must have been in the Spring of 1970, about the only time I would have worked low altitude in ZJX. Somewhere, perhaps 40 miles north of CHS, the ’310’s transponder target disappeared. I gave him the usual spiel to recycle his transponder, but he never replied. Of course, being low altitude, I could still see his primary target and kept tracking him until the target disappeared a few miles later. I had probably alerted the supervisor before this, although I don’t now recall whether that was standard procedure at the time. I probably would have done it as it was my first experience. After about an hour we got a call from FLO FSS that the pilot had experienced electrical failure and being in VMC had elected to land at a nearby airport, from where he called FLO. It was a learning experience for me, because the IFR-lost-comm-in-VMC procedure was one aspect with which I was not familiar.

Fast forward to ZAU and my years in high altitude there. I worked a lot of midnight shifts. I’ve tried to do a rough calculation of how many (50 per year times 30 years equals 1500, but there were many years when I might have worked 100 or more) but can’t quite, although I’m confident it’s more than 1,000. I’ve told people that of that number, I’ll bet I worked 400 that had a lost comm air carrier come through on my watch. Really. It just wasn’t that unusual. In fact, it was so common, whenever ZMP or ZKC would give me the handoff on one and tell me, “he’s not talking to anybody,” I’d laugh and say, “that’s okay, he’ll call when he wants down.” And they always did. We haven’t left one up there yet.

It was easy to understand how it happened. Out west, the ARTCC areas are huge and sectors can be quite large, particularly when they combine up in the late evening. It’s not uncommon for a controller to be working a sector so large he doesn’t have a single frequency which covers it all. Between a controller forgetting to switch his own airplane, to a flight getting “lost” during sector combinations or shift changes, to a flight crew missing a frequency change altogether, there are many ways for a flight to get into the situation NW188 experienced.

For the non-aviation person, it’s important to understand that ATC doesn’t need to be talking to an airplane to separate him from others. For example, oceanic flight entails separation over thousands of miles with no direct conversation with controllers. Any clearance issues that arise as well as routine position reports are handled through adjunct, non-control facilities. In fact, all ATC communications in the ’40s and into the ’50s were relayed through company or contractors. Separation (and the potential for a mid air collision implied) doesn’t depend on being in contact with a particular airplane (massive comm failures at a facility are a different story, however, but that’s an entirely different subject). Moreover, the airplane isn’t lost in the sense ATC doesn’t know where he is—we’re watching him and separating him the whole way.

So, the long and the short of it is, as recently as 1997 (about which I can speak with authority), lost comm flights were not at all unusual, and so far as I can remember, all had happy endings. Usually, at least in the case of these air carrier flights, when the crew gets around to deciding to reestablish contact (when they’re ready to start down) they’ll pull out their chart, find one of the tower frequencies for their destination, and give them a call (the center frequencies are listed on the IFR charts, too, but it can be tricky figuring out which one might be the right one). The tower guy calls us and says, “I have so-and-so on my frequency, who’s supposed to get him?” Information passed, relayed, airplane shows up on the right frequency, and as I remembered, we didn’t even bother to ask where they’d been.

There are a couple of other issues that are more important to me than “where they’d been” in the case of NW188. The first is their clearance limit, which was MSP. Going beyond a clearance limit without clearance is a huge no-no in the IFR system. It’s hard for me to imagine any FMS that doesn’t have a major alarm function when such an occurance is imminent. If there’s anything to truly hang the crew with (and it’s still only a relatively minor pilot deviation), that would be it.

The second is more a curiosity item. Back in the old days, it was not uncommon for the airlines to tanker a lot of fuel—that is, carry much more than required. If they had to fuel up at an airfield which had Jet-A (jet aviation fuel) at a premium price, it made economic sense to limit the amount they took on there by carrying in a half load of cheaper stuff from an other airport. When fuel prices shot up, the cost of carrying extra fuel became more of factor than before, and the bean counters started requiring flights to carry practically the bare minimum of fuel for any trip. It becomes a tricky exercise considering weather, winds-aloft, traffic, and other factors.

I regularly read a blog by a captain at a major airline who on several occasions has addressed that practice. He often likes to fudge an extra 1,000 pounds or so to avoid cutting it too close on the arrival end of the flight (pilots refer to the point at which a flight has just enough fuel to get to the destination as “bingo”). He refers to extended outbound taxiing being enough to require an immediate takeoff at the runway to avoid having to return to refuel—or going Bingo even before takeoff. Being “close” on fuel doesn’t mean running the tanks dry on short final—IFR requires fuel planning to the destination, a 45 minute hold, then enough to fly to the alternate—it’s a matter of being legal. Still, in certain weather conditions, that can still be iffy, and in air carrier operations, winding up Bingo while in flight can lead the chief pilot to call into question a captain’s judgement, putting his career in jeopardy.

I told you all that to raise this question: in today’s airline environment, how did NW188 wind up landing with roughly 10,000 lbs of fuel, even after the extra 200+ miles of flying to get to MSP? That should keep you busy while awaiting answers to the NW188 scenario.




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Last updated: 03 September 2011