HUD labels

Fighter pilots have a well-earned reputation for being rude and crude. Despite that proclivity, they treat their aircraft with great respect as they “yank and bank” them in order to put missiles or bombs on a target. However, they don’t necessarily understand how all the systems in their aircraft work together, enabling them to deliver their ordnance with great precision. They often attribute what goes on in the black boxes as F***’n Magic—FM or Fox-Mike in polite company.

HUD labels

The HUD shows a tremendous amount of information.

FM is most evident in a fighter’s head-up display (HUD), where information is projected in the pilot’s field of view. They can be fixed on the glare shield immediately in front of the pilot or as helmet mounted devices in newer fighters.

HUDs provide basic information like airspeed, altitude, angle of attack, pitch, dive, and bank angles, heading, g-loading, weapon(s) selected, and fuel state. They also present navigation information—direction, distance, and time of arrival—to include cues to speed up or slow down to hit your desired time. They also give steering cues for instrument approaches. Fighter pilots reason FM is the only explanation for how this multitude of information appears in their HUD.

In an air-to-air mode, FM cues pilots where to look for a bandit they’ve “locked up” with their radar. This display can be a target designator (TD) box enclosing the bandit when it’s in the HUD field of view or, when it’s not, a line pointing in the direction of the bandit. All one has to do is look in the direction the line points or else pull the nose of the airplane along the line until the TD box appears in the HUD and, if it’s in visual range, voila, the bandit! Certain symbology rapidly flashing off and on in an F-16 HUD indicated the parameters (range, angles, etc.) for a successful air-to-air shot were met. You could almost hear the FM yelling, “Shoot, stupid!”

FM also helps pilots in the air-to-ground mode with HUD information when employing smart or dumb weapons. It points out ground targets much as it does for a bandit, i.e., puts a TD around it. It also informs a smart weapon where both it and the target are. Merely fly over or near the target (for a powered weapon) and, with your consent, the FM will release the weapon at the right instant to strike the target. Laser guided bombs (LGBs) must be released in a “basket”—think of a funnel with the smaller end sitting on the target. Simply release the LGB high enough at the mouth of the funnel so the FM can “wake up” (the seeker becomes active), detect the laser energy being projected on the target, and then use the LGB’s fins to steer it to the target.

When dropping dumb bombs, FM helps pilots get as close as possible to the required airspeed, altitude, g-loading, dive angle, and offset for winds necessary to accurately deliver them. It’s challenging to nail those parameters while hurling your body at the ground in a 10-45 degree dive going 400-450 knots. Get one factor wrong, and the bomb will not go where it was aimed. If you are steeper, faster, or drop the bomb lower than planned, it will fall beyond the target. When slower, shallower, or you pickle the bomb higher than planned, it will fall short of the target.

The constantly computed impact point (CCIP) mode in the F-16 HUD aids pilots when dropping dumb bombs. The FM-generated flight path marker (FPM) shows where the aircraft will go if all conditions of motion and wind stay the same. A bomb fall line (BFL) connects the FPM and the CCIP (aka “The Death Dot”). F-16 pilots merely maneuver the FPM to drag the BFL across the target and, when the CCIP reaches it, push and hold the pickle button. The FM then goes into overdrive.

With the aircraft radar providing the slant range to the target, the inertial navigation system, GPS, and flight data computer providing airspeed, altitude, dive/bank angle, winds, and g-loading, the FM places the CCIP where dumb bombs will hit if pickled off at a particular point in time/space. For all we knew, the FM studies the ones and zeroes in the system until it sees a solution and, with us holding the pickle button down, releases the bomb at the right moment. Whether you were steeper, shallower, higher, lower, faster or slower than planned, the FM accounted for it all.

HUD

Sometimes the FM dies.

However, sometimes the FM dies. The GPS goes on vacation, the HUD goes to sleep, the INS wanders off to a continent other than the one on which you are currently operating, or your radar takes a smoke-break. In those instances, we Viper drivers were left with what we called an iron sight, which is akin to the fixed, lighted reticle WWII pilots used to aim their weapons. Like those pre-FM sights, our standby iron sight was non-computing. Because others were counting on us, we had to be prepared to get the job done using one.

You are probably asking yourself, “How does this apply to those not flying fighter aircraft?” or, “Why does it matter to me?”

Surely you have noticed FM currently abounds in many aspects of aviation. GPS helps us navigate through or around airspace, make strange field approaches, or fly a SID or a STAR. We even have maps and approach plates pre-loaded into devices so that we no longer have to flip through our FLIP charts and publications to get to our destination.

Are you prepared to handle the situation when the FM dies? Read on to see how I was.

While flying an F-16 no-notice evaluation, I was heading into my target at 500 ft. AGL, going 480 knots to make a radar (no eyes on the target) “toss” delivery of a simulated nuke. I had earlier entered the target’s latitude/longitude into the INS and, on my radar scope, the FM placed crosshairs on what it believed was the target. I fine-tuned that radar picture and designated it, i.e., told the FM that it was definitely on target. The FM then presented a lateral steering bar in the HUD to line me up on my attack heading. I then waited for an FM-generated pitch steering bar to prompt me to climb while I held down the pickle button. In that climb, and when the FM had a solution, it would toss the weapon at the target from several miles away. With the bomb gone, I would fly an escape maneuver—it’s a nuke after all!

However, prior to my pull-up, the HUD blinked once and then went blank. We called our F-16s Vipers but we also called them “electric jets” and, whenever electric-powered things failed, you worried about what caused the problem and what else might fail. While I analyzed the situation, and in case I had to eject, I started a climb to get away from terra firma.

Once I figured out I had a dud HUD, I couldn’t release my weapon without violating our range restrictions. The evaluator radioed that he would grade this event from previous flights on which I made a similar delivery. However, to complete the evaluation, I had to drop some dumb bombs as well as strafe with my 20MM cannon.

I had no excuse to go home as the airplane was still flying and my iron sight was still available. I couldn’t say, “I’m done!”—not now and certainly not if this were a combat situation. My jet would drop my bombs where I aimed them. Our training prepared us for such a situation.

I switched on the iron sight; but I had to set it for each of the three different dive-bomb patterns we were yet to fly. With no FM or HUD information, I had to eyeball the winds and, using the three A (airspeed, altitude, and attitude) round-gauges, get my jet to the required release speed, height, and dive angle, and then manually pickle each bomb. I then had to reset my sight for strafing.

You might ask, “How did you fare?” I’ll tell you.

On sorties flown to a scorable range, fighter pilots had a standard wager: “A quarter a bomb, a nickel a hole.” During the flight debriefing, you plot every bomb dropped. For each bombing pass, every pilot throws a quarter on the table. The one with the best score on each pass wins that pot; winners split the pot when there is a tie. Our standard load was six bombs—on a 4-ship sortie, win every pass and you will earn $4.50. For strafing, the pilot with the most hits wins a nickel for each hole above what the others achieved, e.g., if you got 40 hits, and I got 50, you would owe me 50¢!

HUD helmet on pilot

Are you prepared to fly without all that electronic help?

Drop some good bombs and you could win enough to buy a burger and fries. If you strafed well, you could wash that down with a beer.

Bottom line: I didn’t win enough to buy a burger, fries, or a beer. However, I held my own—I won enough to buy a coke. I also passed the eval! This despite the fact everyone else’s FM was working while mine was D-E-A-D. I had to fall back to the pre-FM days of flying—my training and muscle memory allowed me to get ’er done.

As an F-16 instructor, I encouraged my students to get familiar with the sight picture when delivering ordnance with the FM. They learned why, once they qualified in each gunnery event using the FM, I required them to turn it off and use their iron sight on one mission. HUD video recorders captured every bombing/strafing pass we flew, which allowed us to evaluate each bomb dropped and every strafing pass made—plus we would see if anyone cheated. I never required students to wager on those missions; I only did that with other instructors.

Moral of the story: we should each be prepared for the challenges of pre-FM flying, whether on an eval flight or just taking the family on a Sunday afternoon cruise.

Latest posts by Dale Hill (see all)
7 replies
  1. Cal Tax
    Cal Tax says:

    Interesting and informative, Boots, but I have one comment. The iron site guys were not WWII pilots!! We still used iron sites in the Thuds and Phantoms and all the fighters up to and including Vietnam! No HUD’s in the Thuds or Phantoms I flew but they were just starting to come in near the end of the war in the early ’70’s.
    I sure would have like to have had that magic and we could have done a lot more damage with less sorties if we had that kind of accuracy for all the dumb bombs we dropped.
    Good lesson though, for all pilots—can you fly to your destination and make an approach when you GPS goes dead? Can you still make a VOR/Non-precision approach if you had to? Good to practice shutting off the magic and moving map once in a while and brush up on those old basic skills. What would you do with an electrical failure in the weather? When is the last time you practiced a surveillance approach?
    Good lessons to think about getting too dependent on all the “magic” until it goes away.

    Reply
    • Dale Hill
      Dale Hill says:

      Cal, thanks for the ‘update’ re. what was available in the Thuds, Phantoms, and Huns. Having never flown them, I just used WWII as a place-marker. Our OV-10’s had a reticle that was powered by what could have passed for a night light, and I once worked a TIC with just a grease pencil mark on the HUD as it had chosen to burn out. There was no air support available, so I was shooting my Willie Pete’s into the bad guy positions as I watched tracers and RPGs being exchanged by both sides (the path of the tracers showed me where the bad guys were) and I learned the TIC was broken when the Khmer ground commander told me in his pidgin English, “Oh Nail 49, be careful! They no longer shoot mortar at me, they now shoot it at you!” Sure enough, there were a chain of explosions on the ground that roughly followed my flight path as I circled around to fire another WP.

      Reply
      • John L
        John L says:

        Dale,
        Dumb bombing was all we had in the A-10 when we developed the tactics back in the 70s, so I grew up dumb bombing. I also remember holding feet wet off the coast of VN (in F-4Ds) and hearing a navy lead send his wingman feet wet to jettison his bombs because the magic had failed and he couldn’t dumb bomb. I also remember arguing with Viper drivers at the FWS that they had to learn as a back up when they all said “triple redundancy means never have to worry.” Too bad I couldn’t quote your story back then. Magic is wonderful until it goes poof.

        Reply
        • Dale Hill
          Dale Hill says:

          John, Flew the OV-10 in VN with a light-bulb for a HUD illuminator. The bulb burned out one day and I was called to support a TIC, but our ROE called for an operational HUD to do that. I made a grease-pencil (the FAC’s Swiss Army knife!) mark on the windscreen and broke the TIC with my Willie Pete’s because there was no air available that day. Now, that’s making do with what you have! I also flew the A-10 in the late 70’s (M-B, 355th) and was dazzled when I converted to the Vipers with the FM, but I always worked on my manual deliveries should the ‘what if’ ever happen to me.

          Reply
  2. Karrpilot
    Karrpilot says:

    GPS freezing, headset batteries dying, screens going blank, welcome to my world. I get that time to time flying an old 182. At least I don’t have to worry about bombs or bullets, and someone shooting back. But it certainly does keep me up on old school ways to navigate an aircraft.

    Reply
  3. Don W.
    Don W. says:

    There was a story in Air Facts a while back about an AF cargo pilot flying a timed dead-reckoning approach in IMC into one of the hilltop airfields in VN after a nav radio failure. I learned to fly in the early 1970’s when dead-reckoning and IFR (“I fly roads”) were still a thing.

    In 2002 I was doing refresher and required insurance training with a now defunct flight school out of Austin Bergstrom. My assigned IP was a fresh CFII — a young German national. I could always understand his words, but sometimes his intent was a little more hazy. On the prebrief for our third flight he indicated that he wanted me to navigate under foggles to an airport about 100 miles to the east. Somehow the way he said it caused me to think that I wasn’t allowed to use the GNS 430, VOR/DME, or ADF in the well equipped panel, so I took out a sectional, called for winds aloft, estimated my turn to heading point, time in climb, wind correction angle, etc. He sat there watching and didn’t say anything. We went out to the airplane, and I left the 430, Nav, and ADF off. Once cleared onto the runway, I set the DG to the runway heading, took off, positive rate, foggles down, timer started, turn to heading, climb at desired rate, level off, eyes on the DG and the timer, thinking “This is kinda fun, haven’t done it this way for a long time, don’t want to screw it up…” He just sat there totally silent, watching. Finally, my timer ran out, and I said something like “We should be there”, and he said “okay, take off the foggles”. I did, and couldn’t see the airport. Then I tipped it up on a wing and there she was, right under the wing tip. He looked at me kinda funny and said “Good job! Why didn’t you use the GPS?!!”

    Reply

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