Rockwell Collins’ HGS

Rockwell Collins’ HGS


Rapid advances in cockpit imaging systems promise to accelerate safety improvements, says Dave Calderwood

Synthetic Vision. Enhanced Vision. Combined Vision. Head-Up Display. Zero-Zero landings. Words and phrases you will have heard with increasing frequency in recent years, as aircraft and avionics manufacturers show us a future where flights can take place with greater safety levels, in poorer conditions, than ever before.

But what are these technologically advanced systems? How do they work, and what benefit do they hand to the pilots and passengers? The pace of change in the cockpit means it is sometimes hard to keep track.

No-one has greater experience with these innovations than Rockwell Collins – who pioneered Head-Up Display research and development in civilian ops, and are convinced its next-generation systems will continue to make pilots’ lives easier.

There’s nowhere better to go to see the benefits these systems can bring – and no finer example than to actually just fly using them – than with a flying visit to Rockwell Collins’ HGS HQ in Portland, Oregon.

It’s a great flight from Wichita, Kansas to Portland, Oregon… if the weather is behaving. You set off from rolling plains where it’s incredibly hot, sunny and dry in summer. You cross some of the most spectacular scenery in the world as you fly over northern Colorado, Wyoming, Idaho, and into the lush greenery of Oregon. Of course, if you’re flying IFR at 40,000 feet in a private jet, you won’t see much of the terrain in great detail but you may run into some weather.

The Rocky Mountains, for instance, can attract some serious thunderstorms with the tops of the cells poking above the overcast. You either want to fly over them, if you can, or around. But imagine you are flying in a jet fitted with Rockwell Collins’s next generation of pilot aids featuring in its Head-Up Vision System (HVS), and a flight path indicator will tell you whether you can clear that pesky cell, or whether you need to divert around it.


Coming into Portland International Airport, the weather turns to muck, as it often does so close to the north-west Pacific coast. But the HVS has some more tricks up its sleeve. Not only does it feature the Rockwell Collins Head-up Guidance Sysytem (HGS), but it also has an Enhanced Vision System (EVS) which projects real-time video images onto the HGS.

The EVS uses a multi-spectral camera (meaning it can see much more than the human eye) mounted on the nose of the aircraft. The same HGS also has a Synthetic Vision System (SVS) which gives a 3D picture based on a terrain database in the flight management system. This can also be projected onto the HGS display.

What’s more, you can toggle between EVS and SVS depending on which is more useful at that particular stage of the flight. But there’s another trick – and this is really special – in that you can have both on at the same time to give a Combined Vision System (CVS), right there on the head-up display. It’s a fascinating and insightful look at the flying of tomorrow.

So the SVS synthetic vision tells you what should be out there in terms of terrain and obstacles, giving you a wonderful, lifelike 3D image. And the EVS enhanced visuals are overlaid, seeing through the murk to pick up heat-sourced imagery.

The first HGS-equipped aircraft was a Boeing 727
The first HGS-equipped aircraft was a Boeing 727


There’s a limit to the EVS camera’s ability, mind you. It can’t see for miles and miles, but compared to what the human eye can see in fog and heavy mist, it’s much farther. In an example of how it shows its strength, imagine our jet is on final approach to Portland’s runway 28R, close to the General Aviation side of the airport, and there’s a bit of low level mist swirling around. You’re concentrating on the HGS now, lining up the ‘rifle bore’ sight of the flight path indicator – it literally looks like a rifle sight on the head-up display screen – with the highlighted outline of the runway ahead.

Without taking your eye off the sight, you can also absorb other info displayed alongside. Speed good, almost nil wind which explains the mist, wings level. Suddenly the HGS shows a bright shape on the runway ahead. What the heck? You’re supposed to be cleared to land.

No time to argue… just power on and go-around. As our jet starts to climb away, you glance down and there, lined up on the runway numbers is an Air Force jet. He’d been invisible in the mist – just as the Challenger had been to him – but the EVS infra-red camera had picked up his jet blast, as a bright flash which was displayed on the Head-Up Display screen.

First 727 HGS Install
First 727 HGS Install

Now, this didn’t actually happen for real, but it’s a possible scenario that Rockwell Collins demonstrates on its ground-based flight simulator that’s usually used to show off and fine tune its Head-up Guidance Systems (HGS). The simulator is at its Portland facility – which is Rockwell Collins’ centre of excellence for HGS. It used to be a standalone company: Flight Dynamics started in 1979, bought by Rockwell in 1998, and the name changed in 2006.

Amazingly, to me at least, a total of 6,800 HGS units have been delivered to date, clocking up more than 45 million flight hours, so head-up displays have been around a while.

Many of these HUDs are on commercial airliners, especially for operators using airports which endure more than their fair share of inclement weather. Alaskan Airlines, for instance, started using the then Flight Dynamics HUD on its Boeing 727s back in 1985 in Cat III approaches and landings. That system was the HGS-1000.

HGS 727 Installation
HGS 727 Installation

These days, the Rockwell Collins HGS is standard equipment on many large jets, including the latest Boeing 787 Dreamliner. Its HGS-5000 system – the first to be fully digital – is integrated with the aircraft’s ‘Heads-Down’ instrument panel to minimise duplicated equipment.

Business jets have also embraced the Rockwell Collins/Flight Dynamics HGS, starting with the Dassault Falcon 2000 and 900EX back in 1996/7. Dassault incorporated a later version into the Falcon 7X’s EASy cockpit in 2006, while it also became an option for the entire Gulfstream fleet from 2009.

The latest and most sophisticated versions of the HGS now certified and flying revenue services in business jets are fitted to Bombardier’s Global Vision cockpit being rolled out across all its aircraft, and Embraer’s new Legacy 500. Both aircraft have SVS and EVS available through the HGS, though not yet as the next-gen Combined Vision System view: that step forward has yet to be certified and there are significant challenges to be overcome.

So is it all about added safety, or are there other benefits? Looking at those safety improvements, there is significant evidence that using HGS can reduce the possibility of an accident. The highly respected Flight Safety Foundation investigated 983 accidents and released a report in 2009 that said HGS would have “highly likely or likely prevented” 373 of those accidents, most of which were in the Takeoff & Landing stages.

Flight Safety

A significant number – 70 – might also have been prevented during “Loss of Control” which is usually attributed to an Unusual Attitude or Upset Recovery.

Second, there are “Landing Credits” to be gained through the use of a Head-up Guidance System. In other words, Lower Operating Minima. Already there have been gains but HGS with a Combined Display of EVS and SVS, along with all the other benefits of these new systems, might lower these even further.

These Lower Operating Minima are important around the world to avoid diverts and even cancelled flights, but nowhere more so than in China. The rapid growth of air transport in modern China has put pressure on airports which may only have Cat 1 instrument approaches. Aircraft equipped with HGS can take advantage of “Special Cat 1” operations which give minima down to 450 metres RVR and 45 metres Decision Height.

So far seven airports in China have Special Cat 1 available but it’s expected to be rolled out across more. The Civil Aviation Administration of China (CAAC) is encouraging airlines (and business aviation operators) to install the technology on their fleets. The “China HUD Application Roadmap” calls for 10% of capable in-service airline fleets to be equipped with HUD by 2015 and on all airline aircraft where HUD is offered by 2025.



What are the benefits of Rockwell Collins’ Head-up Guidance System?

I’ve already talked a bit about the Flight Path Indicator which shows where the aircraft is going. So if the Flight Path Indicator is showing touchdown to the right of the runway centreline, then it’s likely there’s a crosswind from the left pushing the aircraft sideways.

Working with the Flight Path Indicator is the Guidance Cue which uses landing aids such as ILS or RNP to compute and position the Cue. Place the Flight Path Indicator over the Cue and you’re on the right approach. It’s very useful when making that crosswind approach. Pilots are used to making crosswind corrections using their own human judgement. HGS helps that by showing you where the aircraft is going, taking the wind into account.


A clear example was on a flight in Rockwell Collins’ demo Challenger 600 where the pilot flying (in the left seat) was judging the approach manually. For me, in the right seat looking through the HGS demo system it looked as though we were drifting right of the runway. Of course, I didn’t have control of the aircraft to correct this but as we got nearer the runway, the Flight Path Indicator came closer to the runway centreline as the pilot flying made more manual adjustments.

Later I would “fly” a similar situation in a sim, with a crosswind dialled in by the the sim operator at the controlling computer. It’s remarkable how accurate and steady it makes the approach when all you have to do is keep the Flight Path Indicator on the preferred touchdown point.

One reason pilots are encouraged to use the HGS throughout all phases of flight is that it takes the guesswork out of certain situations. For instance, there’s a line going left to right across the display: it’s the Zero Degree Pitch Reference which is a sort of Artificial Horizon – except that at high altitude the curvature of the Earth intervenes. Simply place the Flight Path Indicator on the Pitch Reference line and you’re in level flight.

There are indicators to enable precise airspeed control, the Acceleration Caret, which shows the instantaneous energy state of the aircraft, and the Speed Error Tape, which shows the actual speed versus the selected speed – i.e. are you fast or slow? Too slow and decelerating and you’d better add power or dip the nose, and vice versa.

Other tricky situations also get flagged up. For example if the HGS detects windshear then it doesn’t mess about – the word “WINDSHEAR” appears on the display at the top, plain to see.


Windshear can also induce an Unusual Attitude and in this situation, the HGS display reverts to a simple version to help the pilot concentrate and realise what the situation is – and how to return to stable flight as quickly as possible. There’s also a useful Angle of Attack indicator.

Another aid to assist in times of potential hazard is how the HGS shows a safe “Fly To” zone when the Traffic Collision Awareness System (TCAS) picks up a conflict. The pilot simply has to steer the aircraft into the “Fly To” zone and the HGS has already taken into account rates of descent or climb. It’s significantly easier for the pilot flying to work out what to do in what is sometimes a high workload and stressful situation.

As the Flight Safety Foundation research showed, a head-up display can help prevent landing accidents. The new HGS goes further than simply helping the pilot see ahead when it comes to the actual landing, and can even compute when you’re heading for a tailstrike – something which happens more often than you might think.

The HGS Tailstrike Avoidance system will give a warning in time for the pilot to perform a safe go-around, useful because in a tailstrike the aircraft is usually too close to the ground to take any other action. Most Boeing 737 operators will have had a tailstrike, but with HGS fitted it simply doesn’t happen.

BENEFITS OF HGS Without HGS, touchdowns are scattered both vertically and further from the centreline.
Without HGS, touchdowns are scattered both vertically and further from the centreline.

A study by Rockwell Collins shows how touchdowns and roll-outs are much more accurate with HGS, claiming that 95% of touchdowns are within 900 to 1200 ft of the threshold, and 99% within 30ft of the centreline – both figures much better than without HGS. Of the 51 flights studied with HGS, there were no go-arounds. The 52 flights monitored without the system saw touchdowns scattered both vertically (along the runway) and further from the centreline with six resulting go-arounds. Finally, once you’re on the ground the HGS brings up an intuitive graphic that shows runway remaining, especially useful for a roll-out on a wet or contaminated runway.

So when is a full Combined EVS + SVS Head-up Guidance System likely to become available, with its accompanying benefits and especially landing credits? Although Rockwell Collins is a long way down the route with the technology, especially the difficult part of integrating the Enhanced Vision System real-time video image with the Synthetic Vision System generated graphics, there are still some challenges to be overcome. One important technical issue being tackled by Rockwell Collins is that airports are changing to LED runway lighting, over cost and environmental concerns. LEDs use less electricity for the same or better brightness and are also more reliable than conventional bulbs. Previous EVS cameras could not pick up the lower temperature of LEDs, but the EVS-3000, developed by Rockwell Collins, brings the Head-up Vision System a step closer, For regulators such as the US FAA, Europe’s EASA, and China’s CAAC, to approve and certify a Combined Vision System Head-up Guidance System, and allow the Lower Operating Minima, all the technical challenges have to be overcome and demonstrated through an intensive set of flight tests. The best estimate by Rockwell Collins’ top guru on HGS, Bob Wood, who started with Flight Dynamics right back at the beginning, is “four to five years”.


The most visible and important part of the Head-up Guidance System is the screen itself, which sits in front of the pilot’s face and is a bit like a drop-down sun visor.

It can be stowed away but increasingly pilots are being urged to use the HGS all the time – not just on approaches. It takes a little time to adapt to using the screen which has a translucent green tinge allowing you to see through it to the world outside.

You also have to have your head and eyes in the right position to see the image and data being displayed on the screen, so you don’t want to be concerned about getting this right at crucial stages of the flight. Besides, there are many functions of the HGS which are useful in the cruise.

The images and data on the green screen are projected from a unit above and slightly behind the pilot’s head. In turn, this receives its info from the HGS computer which is taking inputs from a variety of systems, including the EVS camera and aircraft’s Flight Management System. The latest versions of the HGS are being fully integrated into the aircraft’s system with the most up-to-date example being Boeing’s 787 Dreamliner.

For business aircraft, the HGS is integrated with Rockwell Collins’ Pro Line Fusion integrated avionics which is at the heart of Bombardier’s Global Vision cockpit (and other manufacturers).