Optical illusions in the murk

[azure]

I had an eye-opening experience today. I needed to fly a hold to prevent my currency from lapsing at the end of this month (flew 6-ITS last month, needed the 'H'), and this morning was perfect, benign IFR conditions, so I filed a local IFR to shoot the RNAV into home base. Once airborne and IMC I asked for and got cleared to fly the approach with the HILPT, did the turn, passed the FAF, came down the advisory GS and broke out at around 1500 MSL (800 AGL) even though the AWOS was reporting OVC012 and 7SM. I let myself settle down to about 1400 before trying to spot the runway (stepdown minimum is 1360), and thought I could make out the runway and started to aim for it, still holding my altitude. After 10 seconds or so I realized it was NOT the runway -- mainly because I know what the runway at VLL looks like. But I still thought it was something on the field, likely the hangar rows, as it appeared to be the right distance away. But the runway should have been to the left of the hangars, and there was no runway there. At that point I had a moment of confusion and went back on the gauges. I was one dot right at that point so corrected and held firm just under 1400. Eventually I realized that the "runway" was a vertical column of windows on a high-rise in Birmingham! The murk had created a nice optical illusion and I could easily imagine a pilot who was unfamiliar with the field getting fixated on that illusion and crashing (or nearly crashing) into the building. In a few seconds, the runway appeared out of the murk right where it was supposed to be. If it hadn't, I was spring loaded to go missed as the ground features looked unfamiliar enough that I was starting to doubt the instruments.

Until today I would have considered asking for a contact approach at home base if I really needed to get in. I've learned that lesson, it's too easy to be fooled by an illusion. If you're not sure, go missed and either try again, or better, fly to an alternate, preferably one with a nice ILS or LPV.

 

[Jaybird180]

You'd think they'd get that highrise out of the way.

 

[azure]

You'd think they'd get that highrise out of the way.

It's not remotely in the way. It's well below the approach path and about a mile south. I was flying slightly crabbed at that point, which contributed to seeing a point off to the side as being dead ahead. It only got in the way when I aimed for it -- my mistake. I should have stayed on the gauges until I was 100% sure.

It probably should be charted though. ISTR there was once a charted obstacle near that position that explained the stepdown -- my guess is the stepdown is due to that building, but for some reason it's no longer charted, or I'm remembering incorrectly.

 

[Jaybird180]

There is a 905ft obstacle right on the FAC after ZAVMO on the plan view. Is that what you mean?

 

[Capt. Geoffrey Thorpe]

You'd think they'd get that highrise out of the way.

More likely, the airport would go the way of other airports in the area (Big Beaver for example).

 

[gismo]

I had an eye-opening experience today. I needed to fly a hold to prevent my currency from lapsing at the end of this month (flew 6-ITS last month, needed the 'H'), and this morning was perfect, benign IFR conditions, so I filed a local IFR to shoot the RNAV into home base. Once airborne and IMC I asked for and got cleared to fly the approach with the HILPT, did the turn, passed the FAF, came down the advisory GS and broke out at around 1500 MSL (800 AGL) even though the AWOS was reporting OVC012 and 7SM. I let myself settle down to about 1400 before trying to spot the runway (stepdown minimum is 1360), and thought I could make out the runway and started to aim for it, still holding my altitude. After 10 seconds or so I realized it was NOT the runway -- mainly because I know what the runway at VLL looks like. But I still thought it was something on the field, likely the hangar rows, as it appeared to be the right distance away. But the runway should have been to the left of the hangars, and there was no runway there. At that point I had a moment of confusion and went back on the gauges. I was one dot right at that point so corrected and held firm just under 1400. Eventually I realized that the "runway" was a vertical column of windows on a high-rise in Birmingham! The murk had created a nice optical illusion and I could easily imagine a pilot who was unfamiliar with the field getting fixated on that illusion and crashing (or nearly crashing) into the building. In a few seconds, the runway appeared out of the murk right where it was supposed to be. If it hadn't, I was spring loaded to go missed as the ground features looked unfamiliar enough that I was starting to doubt the instruments.

Until today I would have considered asking for a contact approach at home base if I really needed to get in. I've learned that lesson, it's too easy to be fooled by an illusion. If you're not sure, go missed and either try again, or better, fly to an alternate, preferably one with a nice ILS or LPV.

Now you know how highly experience professional crews have managed to land a the wrong airport. Granted that's not the illusion you had but from a mental perspective it's pretty much the same thing. When the picture is unclear you see what you expect to see if there's anything close to what you're expecting.

The cure is to maintain a watch on your navigational guidance until you're on short final (i.e. 200-300 AGL) regardless of whether or not you think you see a runway. Have you ever managed to line up with Hwy 59 when landing to the west at PTK? (I have).

 

[Captain]

I'd offer this.

Fly more instruments. If you're going to dive and drive be aware you're below GP. If you're going to VNAV be aware of that and there shouldn't be a level off. It appears you hit 1400 well before ZAVMO and off centerline to boot.

So, whilst in the soup be more diligent in both vertical and lateral navigation. Make a plan and fly it exactly. Don't forget about crab and know where to look when you do break out. That runway should have a nice PAPI on the right. Did it? Were you looking for it?

Anyways, you survived and it's a learning experience. Good story to share. Well done.

 

[azure]

There is a 905ft obstacle right on the FAC after ZAVMO on the plan view. Is that what you mean?

It's not what I meant, but it's possibly what I was thinking of. Somehow I thought there was a somewhat higher charted obstacle right of course at or slightly before ZAVMO. But maybe I'm imagining that.

 

[azure]

Now you know how highly experience professional crews have managed to land a the wrong airport. Granted that's not the illusion you had but from a mental perspective it's pretty much the same thing. When the picture is unclear you see what you expect to see if there's anything close to what you're expecting.

Yup, exactly.

The cure is to maintain a watch on your navigational guidance until you're on short final (i.e. 200-300 AGL) regardless of whether or not you think you see a runway. Have you ever managed to line up with Hwy 59 when landing to the west at PTK? (I have).

No, but I've never landed there to the west from IMC on anything but the LPV, which takes you so far down there's no chance of mistaking M-59 for the runway. On the LOC BC, I could definitely see that happening.

 

[azure]

Fly more instruments. If you're going to dive and drive be aware you're below GP. If you're going to VNAV be aware of that and there shouldn't be a level off. It appears you hit 1400 well before ZAVMO and off centerline to boot.

Oh, I was aware I was below GP. It wasn't exactly dive and drive, more of a hybrid. You may not know that they they redesigned the approach a couple of years ago. The MDA used to be higher but there was no stepdown. The advisory GS was more useful then, you could fly down to MDA as if it were an LPV. Apparently they decided there wasn't enough obstacle clearance that way. At any rate I no longer follow the GS all the way down, but transition to straight LNAV before reaching the stepdown altitude.

Also, I was dead center when I broke off, and only got off course when I aimed for the building. That was my mistake, as Lance said I should have remained on the GPS for navigational guidance even when I thought I had the runway made.

So, whilst in the soup be more diligent in both vertical and lateral navigation. Make a plan and fly it exactly. Don't forget about crab and know where to look when you do break out. That runway should have a nice PAPI on the right. Did it? Were you looking for it?

Obviously you're not familiar with the field. That PAPI is basically invisible in daylight until you're about a mile out, or more in haze. I was about 3-3.5 nm from the threshold at that point. So no, I wasn't looking for the PAPI.

You're right about taking crab into account, that was another mistake I made.

Anyways, you survived and it's a learning experience. Good story to share. Well done.

Thanks, definitely a learning experience!

 

[gismo]

No, but I've never landed there to the west from IMC on anything but the LPV, which takes you so far down there's no chance of mistaking M-59 for the runway. On the LOC BC, I could definitely see that happening.

Yes it was the LOC BC (many years ago). And I'd grown complacent about maintaining the centerline on the BC since it goes kaflooy when you get close.