Aircraft manufacturers have a new choice for sourcing a head-up display (HUD) for their business jet flight decks: Garmin’s GHD 2100. Certified on Textron Aviation’s Garmin G5000-equipped Citation Longitude, the GHD 2100 is a fully capable HUD matched to an Elbit multi-sensor camera system and offering traditional HUD as well as enhanced, synthetic, and combined vision system imagery.
The HUD landscape has been dominated by Collins Aerospace, which bought Head-up Guidance Systems manufacturer Flight Dynamics in 1999 and manufactures HUDs for aircraft equipped with its avionics and for Gulfstream jets with Honeywell Epic-based flight decks. Elbit also manufactures HUDs, and Dassault is the primary business aviation customer, having been first to market with a combined vision system (CVS) overlaying synthetic vision system (SVS) and infrared enhanced vision system (EVS) imagery on the HUD. The GHD 2100 includes CVS as do some modern Collins systems installed on Bombardier and Gulfstream jets.
There is also the SkyLens wearable HUD developed by Elbit’s Universal Avionics subsidiary, and this has distinct advantages for aircraft where there is no space to install a full-size HUD projector or for operators that want more functionality than a traditional HUD. While Honeywell made its own HUD many years ago, that product never took off, but the company recently purchased HUD assets from Saab and is now developing a new line of HUDs.
HUDs, which have been a mainstay in military aircraft for decades, have grown in popularity in the business aviation market since Gulfstream pioneered installations in its large-cabin jets. It was first to offer EVS, in 2001, which eventually enabled enhanced flight vision systems (EFVS), and then was followed with SVS imagery on the HUD.
A business jet HUD allows pilots to view important flight information on the combiner glass mounted in their forward view while also enabling them to look through the combiner at the outside world while focusing on everything except the glass in front of their face. This eliminates the need to look down at a primary flight display (PFD) and then back up through the windshield, and HUDs are especially helpful during final approach, with EFVS enabling approaches to lower minima by helping pilots see runway lights earlier than with the naked eye.
On the GHD 2100, pilots can see conformal attitude and flight path information, navigation data, autopilot modes, and master warning/caution annunciations.
Garmin’s HUD is an option for the Longitude, available either standalone or as part of an EFVS when the Elbit camera is installed. Most buyers will likely select this option, which is priced at $668,700, and the take rate has thus far been about 25% of non-fleet Longitude buyers.
While designing the complex optical elements that make up a HUD is a significant challenge, Garmin engineers were able to keep the HUD projector that mounts on the cockpit ceiling above the left-seat pilot relatively slim, so it doesn’t impinge on headroom. The HUD’s field of view is 30 degrees horizontal by 24 degrees vertical, and like all HUDs, it does require careful positioning of the seat to keep the images on the combiner glass clearly in view. I didn’t find it difficult to set up for my viewing comfort.
The GHD 2100 was certified as part of the Longitude’s type certificate in 2023. Textron Aviation is seeking up to 50% visual advantage approval, allowing landings with lower visibility—cutting it from a half to one-quarter of a mile. With EFVS, the GHD 2100-equipped Longitude can already descend to 100 feet above touchdown-zone height.
Textron Aviation manager of flight operations Rip Lee flew the demo flight with me and, sadly, the weather didn’t cooperate; it was clear blue skies in Wichita, Kansas, so I wouldn’t get to experience the HUD in poor weather. Luckily, we were able to schedule some time in Textron Aviation’s Longitude iron bird engineering simulator, which precisely replicates the flight deck and control feel of the real airplane. The simulator would allow us to set some lousy weather so I could see how the HUD performed in adverse conditions.
Flying the Iron Bird
Peter Fisher, senior engineering test pilot and the head of the HUD certification program, walked me through the HUD demonstration in the engineering simulator. After taking off, I did some airwork including steep turns, then he had me climb steeply to see the arrows on the HUD pointing down and showing me which way to move to recover. I tried the same in a steep 80-degree turn to the left, and arrows pointing to the right popped up on the HUD.
With a precision approach dialed in, I hand flew to landing with weather set to one-quarter-mile visibility and using the Longtitude’s autothrottles. This was the first time I saw Garmin’s new lead-in line chevrons with their associated mile markers, a great improvement to the G3000/G5000 avionics suite and viewable on the HUD or PFD.
Pilots can choose which mode to view on the HUD using a dual concentric knob mounted just to the right of where the combiner hinge is attached to the projector. Turning the small knob switches between EVS, SVS (Garmin calls it synthetic vision technology), and CVS. The large knob is used to adjust brightness. More options are available on the Garmin touchscreen controller’s PFD settings. One includes the ability to switch off SVS terrain so obstacles around the airport or in the foreground are still visible but distant terrain isn’t depicted. This offers a cleaner view, but I like seeing the terrain so I probably wouldn’t use this too often.
The CVS mode superimposes EVS and SVS, but there is a cutout that eliminates SVS on the runway and approach lights. I found that this helped me focus on where the approach lights should appear, and during the low-visibility approach, I could see the lights on EVS well before my eyes could see them without EVS. With this system, the HUD can detect LED lights that are becoming more widespread on runways, thanks to the multi-spectral sensors of the Elbit camera.
To help pilots through the landing, the HUD automatically declutters when approaching the runway, eliminating the horizontal situation indicator when gear and flaps are lowered, and it pops up flare cues (plus signs) to help the pilot achieve a smooth and accurate touchdown.
Fisher repositioned the simulator over Geneva, Switzerland, where I flew toward mountains until a TAWS alert told me to pull up. Flying an approach into Geneva, we couldn’t get vertical guidance to work but this just demonstrated one of the HUD’s benefits; I just put the flight path vector in the HUD over the aim point on the runway, resulting in a perfectly stable approach.
Airborne with the GHD 2100
I’ve flown the Longitude twice before, so it was somewhat familiar. But this was the first time with the HUD. Sitting in the Longitude’s left seat, I didn’t find that the HUD projector impinged my headroom. In any case, it is mounted behind where the pilot’s head should be once the seat is adjusted.
Spotting a HUD-equipped (EFVS) Longitude is easy: just look for the camera mounted on the upper nose. It is carefully positioned to line up with where the left-seat pilot is looking to eliminate parallax. The GHD 2100 is fully conformal, which means that what you see in the combiner glass accurately matches the outside world.
With Rip Lee in the right seat and Textron Aviation chief pilot Shane Reese in the cabin, I used the Longitude’s tiller steering to taxi to Eisenhower National’s Runway 19L, maintaining the proper taxi pace by referring to the groundspeed displayed on the HUD. After pushing the go-around button to set the flight director for takeoff, I taxied onto the runway and advanced the throttles until the autothrottle system took over. Once in the air, I set the nose attitude to match the pitch box in the HUD and climbed to 12,500 feet for some airwork.
After getting used to the feel of the Longitude again, I flew some steep 180-degree turns, which are even easier with the HUD; just put the flight path vector on the zero-pitch line, far simpler when looking through the HUD and windshield compared to having to look down at the PFD.
I then slowed down for some low-speed maneuvering. In clean configuration, I slowed straight ahead, then in a left bank, followed by straight ahead with landing gear and flaps in landing configuration. Each time, I watched the Garmin autopilot engage the autothrottles, advancing power and lowering the angle of attack to prevent a stall. I was using the HUD almost the whole time and rarely let my eyes range over the flight and multifunction displays.
We dialed in the RNAV (GPS) 13 approach at Hutchinson Regional Airport where I hand-flew, following the guidance on the HUD with CVS on, all the way to touchdown using the flare cue. The landing was smooth but we did touch down left of the centerline, which may have been due to watching the HUD imagery and not looking through the HUD at the actual runway.
After taking off, I kept the Longitude low and turned left toward some tall towers so I could see what they looked like in the HUD’s CVS. The synthetic vision system painted them clearly so they were easy to spot.
For the second landing at Hutchinson, Lee input the visual approach to the runway. This time I tapped the CLR button on the yoke to remove the SVS and EVS imagery from the HUD so it just had the flight information. With the flight path vector on the aiming point, the Longitude descended steadily to the runway and another smooth landing using the flare cue.
For our final approach to Hutchinson, I headed north after takeoff and then lined up for the Runway 22 approach, using the GPS overlay with lateral and vertical guidance instead of the plain VOR approach. I wanted to try an autopilot go-around, so I let the autopilot fly the approach. With landing gear and flaps down, at about 300 feet, I pushed the go-around button on the power lever, and the autopilot disengaged while the autothrottles advanced the power. I followed the flight director guidance on the HUD as Lee retracted the landing gear and flaps and then set flight-level change and heading modes on the guidance panel.
Returning to Wichita, we were lined up for a right base to Runway 19L so we set up a visual approach and selected approach mode, which provided lateral and vertical guidance. I was flying a little nose-high on short final, but the flight director guidance was spot on as I matched the flight path vector on the flight director donut by pushing the nose down, and then it was time to follow the flare cue for a landing that was almost right on the centerline.
So far, Textron Aviation hasn’t announced any other jets that might be equipped with the GHD 2100 HUD. Garmin is offering it to other aircraft manufacturers as well, and the HUD can be integrated with non-Garmin avionics, according to the company.
Slowly but surely, Garmin has paved its way into larger aircraft with sophisticated integrated avionics systems, and the addition of a capable and relatively space-saving HUD is a significant accomplishment.