Heads Up on Heads-Up: SDO hazards from moving-tape HUD symbology

Flying Safety, June, 2002 by Jeff Long

Spatial Disorientation (SDO) has been killing fighter pilots for many years. This time it claimed a student of mine (for his family's privacy, let's call him Steve, a completely fictional name). Steve died at night in an F16 shortly after takeoff. Although he had planned to accomplish night intercepts, he died before his Flight Lead even said "Fight's On." The Flight Data Recorder shows he became spatially disoriented during a benign navigational turn and remained so all the way up to his belated ejection attempt.

It saddens me when I hear about any fatal accident, even more so when the fallen aviator is a peer or acquaintance. The emotion reaches a different level, I've found, when the victim is someone you've taught to fly. At SUPT graduation, Steve's class presented me a plaque with a class photo on it. Now, whenever I look at it, I wonder what my fellow instructors and I--or the Air Force as a whole--could have done to save his life.

Reducing SDO Mishaps

From a training standpoint, the Air Force already does much to minimize the effects of SDO. Aerospace physiology specialists train students in equipment that produces vestibular illusions. Instructor Pilots teach unusual attitude recoveries in both the T-37 and T-38, not only in the aircraft but also in the simulator. We use vision-restricting devices in the aircraft to safely give students experience in trusting their instruments more than their inner ear. The Air Force is currently looking into buying newer and better SDO trainers. Given the impressive efforts already being made, there don't appear to be easy any ways left to make huge strides via training.

Another approach through which the AF is striving to reduce SDO deaths is by improving how we equip our fighter pilots. This article will focus on that effort by explaining how improvements to the way Head-Up Display (HUD) airspeed and altitude information is displayed should make the F22 and F-35 safer than the older-technology aircraft they replace. These new aircraft use Counter-Pointer (C-P) displays rather than the Moving-Tape (M-T) displays found in the F-15, F-16 and A-10.

Like most groups of people, fighter pilots can be resistant to change. Resistance is usually fiercest when people don't understand the reasons the change was initiated. My objective in writing is to inform fighter pilots and fighter/bomber-track SUPT instructors about why the "Military Standard" HUD found in the F-22, F-35 and T-38C looks different from older HUDs (see F-22 HUD in figure 1).

Before I begin, let me add one caveat: My comments are intended to relate primarily to combat aircraft and to the training of pilots who fly them. I know very little about the air mobility business, but enough to point out that mobility aircraft are not designed to fly at extreme attitudes, to pull high-G turns, or to be flown by only one pilot. All three factors make mobility pilots' SDO risk experience different. Some mobility aircraft now have HUDs, and I will defer comment on what symbology is appropriate for them to people more knowledgeable about the mobility business.

Many readers may be asking. "If it ain't broke, why fix it?" In answering, I'll cover both general flight safety information and Human Factors (HIP) information, and then I'll tie the two areas together by examining a mishap in detail.

Flight Safety Information

Shortly after I learned of Steve's death, I started the Flight Safety Officers' Course at The Air Force Safety Center at Kirtland AFB. I resolved to use the resources of the safety system to learn more about this mishap. While there, I met AFSC's leading Aerospace Physiologist, Lt Cal Don White, who, as it turned out, had already done a relevant analysis. His examination of long-term mishap trends (see Table 1) revears a downward stoping trend for G-induced Loss of Consciousness (GLOC), but an essentially flat one for SDO. This suggests that the aggressive campaign the Air Force has been waging against GLOC is meeting with some success, and that we need a similarly aggressive campaign on SDO.

Lt Col White's study, combined with the fact that Steve had died in an F-16, motivated me to review every fatal F-16 mishap from 1 Oct 1991 to 1 Jul 2001 (see Table 2).

I found two things particularly noteworthy. First was the large proportion of fatal mishaps caused by SDO. In fact, SDO turns out to be the number one killer of F-16 pilots. Second, although most of those SDO mishaps occurred during "tactical" phases of flight such as night delivery of Laser-Guided Bombs, an alarming number (12 of 36) occurred during "admin" portions of the mission--benign events such as a fluid turn prior to "fight's on," or an instrument approach. Some things fighter pilots do are inherently dangerous; that list shouldn't include admin.

Speaking of deadly admin, let's get back to Steve. He entered a fluid turn. He looked too long through his Night Vision Goggles (NVGs) at his flight lead and failed to adequately cross check his HUD or head-down instrument panel. He became disoriented, and eventually reached approximately 70 degrees nose low and 150 degrees of left bank.