How Can a Commercial Airliner Land at the Wrong Airport?

[Ivan Seeking]

ST. PAUL, Minnesota (AP) -- A Northwest Airlines flight that was headed to Rapid City, South Dakota, landed a few miles off course at Ellsworth Air Force Base, and passengers had to wait in the plane for more than three hours while their crew was interrogated. [continued]

http://www.cnn.com/2004/US/Central/06/20/wrong.airport.ap/index.html

So how can this happen? With the control tower in Rapid City watching the flight on RADAR, and since I thought the pilots always communicate with the tower before landing...? Also, I am told that commercial jets usually land on auto-pilot now.

A similar thing thing happened in Van Nuys, Ca, some years ago. A commercial jet landed at an airport only for relatively small, private aircraft.

 

[russ_watters]

I---L---S.

 

[Imparcticle]

maybe the pilots were taken over by aliens! The aliens are probably just playing pranks on us.

 

[Moonbear]

The scary thing is that for Rapid City, the air traffic control tower is AT the airforce base, so you'd think the AF would know who they were letting land there! They interviewed one of the passengers and I've never heard of such bungling! Once they landed, of course the AF realized they didn't want anyone seeing what was at the base, so told everyone on the plane to shut their window shades, which were of course open for landing, and that they then had to open again at take-off. Okay, so I know that's one of those goofy rules now that the shades need to be open for take-off and landing so they know nobody is being held hostage on-board, but after sitting on the runway for several hours at an airforce base, don't you think they might have been able to make an exception to that rule?

 

[Ivan Seeking]

I---L---S.

My point exactly. I don't see how the glide paths were confused unless the plane somehow locked onto a military beacon. I would think that these systems could not cross over.

 

[chroot]

I'm sure that both the civilian and AF bases have ILS systems. It's entirely possible -- though entirely ridiculous -- that the pilots simply looked up the wrong ILS frequencies on their sectional chart during their pre-flight planning. It seems the ILS for KRCA (Ellsworth) Runway 31 operates on 110.30 MHz, while the ILS for KRAP (Rapid City) Runway 32 operates on 109.30 MHz. The frequencies differ only by a single digit, so a simple entry error might be to blame. Rapid City's Runway 14 (the same runway as 32, just in the other direction) does not have an ILS approach.

Commercial aircraft do indeed fly to decision height automatically on a Class 3 approach. If they were on the ILS in clouds, it is possible that they just never realized they were on the wrong approach -- and once you're close enough to make visual with a runway, it's pretty hard to tell what airport you're at -- runways all look pretty much the same. These two runways, however, are not numbered the same -- the regional airport's runway is 14/32, and the AFB's runway is 13/31. The pilots should have noticed this when they made visual and done a missed approach, but, well, frankly... you land at so many airports so many times, you don't really think to check the number on the runway after you've completed a clean ILS approach!

The tower is not in continuous contact with the pilots during a landing -- they clear the aircraft for an ILS approach, but that's about the end of their involvement. Rapid City's 32 ILS does have an outer marker, called "Ranch," that most pilots would report crossing. They may not have worried about crossing the outer marker, or they may have thought it was malfunctioning. Since the two airports are so close, it's actually conceivable that they may have crossed KRAP's outer marker as expected even while on the localizer for KRCA. I'd have to have approach plates for the area to verify this, but I don't have them (I don't live in SD!).

You'd have hoped that the pilots would have noticed all of the other information that their plane was giving them to indicate they chose the wrong ILS -- their heading would have been wrong, their GPS should have giving them a large course deviation indication, etc. They may not have been using those tools properly, however, or at all. Keep in mind that virtually all aviation mistakes are 100% pilot error.

While there doesn't seem to be an NTSB report on the mishap yet -- and perhaps there won't ever be one, seeing as it didn't really qualify as an accident -- I would bet money that the pilots just entered the wrong ILS frequencies into their instruments.

- Warren

 

[Ivan Seeking]

It seems the ILS for KRCA (Ellsworth) Runway 31 operates on 110.30 MHz, while the ILS for KRAP (Rapid City) Runway 32 operates on 109.30 MHz. The frequencies differ only by a single digit, so a simple entry error might be to blame. - Warren

That must be the culprit; at least it is easy enough to see happening.

 

[chroot]

Keep in mind that, in most avionics, knobs are used to dial in frequencies -- it's possible that they just went one click too far.

- Warren