52nd Fighter Wing modifies runway at Spangdahlem to reduce optical illusion

Stars and Stripes ^ | February 13, 2008 | Scott Schonauer

[Jet Jaguar]

SPANGDAHLEM AIR BASE, Germany — Seeing is not always believing.

For years that has been the case at Spangdahlem Air Base, where pilots have had to cope with a potentially dangerous and well-known optical illusion when approaching the runway.

The approach has long been considered risky, but the Air Force has made changes to the airfield to reduce the illusion in hopes of improving safety. Last year, crews added a dark epoxy coating to the ends of the runway and shifted antennas about 10 meters. The changes cost more than $1 million and were finished up last October. The base also completed a $3 million resurfacing job last year.

The illusion stems from the runway’s incline. When approaching the base from the southwest end, the runway has an upslope that makes pilots erroneously believe the aircraft is coming in too high. The natural response is to reduce altitude to compensate for the illusion. The exact opposite phenomena occurs when a pilot approaches a runway that slopes down.

It is the first time the Air Force has made such changes to one of its runways, and engineers had to get special permission to add the coating, said Lt. Col. Kathryn Kolbe, 52nd Civil Engineering Squadron commander. But a unique solution was needed for a unique flight hazard, officials said.

The 52nd Fighter Wing made the alterations after an investigation into an F-16 crash on Sept. 14, 2006, found that the “visual illusion,” in addition to the previous location of the antennae, contributed to the accident.

There have been at least seven incidents since the mid-1970s in which Air Force planes have either hit short of the runway or hit an antenna at the end of the runway, said Lt. Col. Tony Forkner, 52nd Fighter Wing chief of safety. The weather and the fact that the runway appears to be on a plateau because it is surrounded by valleys only add to the potential dangers.

“The runway environment here is a very challenging one,” said Lt. Col. Scott Bowen, a pilot and the 52nd Operations Group deputy commander.

A report into the 2006 crash determined that then-1st Lt. Trevor Merritt of the 22nd Fighter Squadron might have been tricked by the illusion. He approached too low, clipping the far field antennae. That damaged his landing gear, forcing him to ditch the airplane near the town of Oberkail. He ejected safely from the fighter.

Pilots flying in and out of Spangdahlem have been warned for years about the illusion in their preflight reports.

By painting the ends of the runway a different color than the gray concrete, pilots will be able to see the correct touchdown point better, Bowen said. Moving the antennas also will create a buffer so pilots who come in low will have a lesser chance of clipping the antennas. Officials hope the changes will help save lives.

“We’ve only improved the airfield,” Bowen said. “We’ve only taken away a significant number of those flight hazards. While I can’t promise that that is what’s going to happen, that was the intent behind all of it.”

[David Isaac]

This Schonauer isn’t any relation to another famous person of the same name, is he?

[Jet Jaguar]

I have no idea. He has been reporting for S&S for a couple of years. IIRC.

[Solitar]

I googled for what percent incline but failed to find it. Does anyone here know what percent slope or incline that runway has? I suspect some civilian stateside runways may have similar slopes.

[Doogle]

...found the end of a Falcon on a search..the report follows

General Dynamics F-16C Block 50B Fighting Falcon
c/n CC-34/36
0337 (F-16CJ, 52nd TW, 22nd FS) struck antenna at Spangdahlem AB, Germany
Sep 14, 2006. Pilot reported undercarriage problem which was still
unresolved when plane became low on fuel. Pilot flew the aircraft
to an open area 10 mi N of base and ejected. Plane crashed near
Oberkail. AFM Nov 2006. An investigation revealed that the
upslope at SW end of runway at Spahgdahlem AB produces
an optical illusion leading pilots to believe that they
are approaching too high, in this case it led the pilot
to descend too soon and strike the antenna, which has now
to be removed. (AFM 3/07)

[Jet Jaguar]

Thanks for the report.

[ovrtaxt]

Shape Constancy

To appreciate how false shape constancy cueing can create orientational illusions in flight, consider the example provided by a runway that is constructed on other than level terrain. Figure 14a shows the pilot's view of the runway during an approach to landing and demonstrates the linear perspective and foreshortening of the runway that the pilot associates with a 3° approach slope. If the runway slopes upward 1° (a rise of only 35 m in a 2-km runway), the foreshortening of the runway for a pilot on a 3° approach slope is substantially less (the height of the retinal image of the runway is greater) than it would be if the runway were level. This can give the pilot the illusion of being too high on the approach. The pilot's natural response to such an illusion is to reshape the image of the runway by seeking a shallower approach slope (Fig. 14b). This response, of course, could be hazardous. The opposite situation results when the runway slopes downward. To perceive the accustomed runway shape under this condition, the pilot flies a steeper approach slope than usual (Fig. 14c).

Figure 14. Effect of runway slope on the pilot's image of runway during final approach (left) and potential effect on the approach slope angle flown (right). a. Flat runway -- normal approach. b. An up-sloping runway creates the illusion of being high on approach -- pilot flies the approach too low. c. A down-sloping runway has the opposite effect.

[Jet Jaguar]

Guams’ runway at Anderson AFB is sloped in a similar way.

I wonder if they have had similar incidents.

[Jet Jaguar]

Andersen AFB. (sp)

[Erasmus]

From Google Earth—

SW end elevation ~1126 ft

NE end elevation ~1179 ft

Length ~10 000 ft

So slope is upward to the NE 53 in 10 000, or .0053, or 0.3 degrees.

BTW, off both ends there are dropoffs on the order of 200 feet. These may be a factor in the optical illusions.

[-=SoylentSquirrel=-]

Oh yeah, looks pretty off kilter to me.