Helicopters operating in the relatively hostile search and rescue (SAR) and emergency medical services realm are being equipped with safety-enhancing avionics, the likes of which in the past were only available on high-end business jets.
A leading solution is Honeywell's Primus Epic, an integrated avionics platform that provides improved situational awareness to the flightcrew and enhanced aircraft handling, flight planning and safety. In short, Primus Epic answers the basic questions that flightcrews ask - what is our present situation, where are we going, where do we want to go and how do we get there - elements that taken together ensure that pilots stay ahead of their aircraft.
Flight International was invited by Honeywell to evaluate the advanced avionics and flight-control systems available with Epic in the company's corporate AgustaWestland AW139. We flew from the company's corporate headquarters in Morristown, New Jersey in November last year.
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In the Primus Epic package, Honeywell has taken the relevant technology it has developed for the fixed-wing world, augmented and updated it to provide not only all the fixed wing capabilities such as fully automatic, hands-off approaches and landings, but also two of the most difficult features to achieve in helicopters - safe SAR at night in bad weather over hostile terrain or very rough seas and emergency medical services, two sectors with high serious accident rates.
The solution is an avionics package that has navigation capabilities including radio altimeters, flight-control systems - including stabilisation augmentation - a four-axis automatic flight-control system, flight director and dual attitude heading reference systems flight management systems, as well a host of other safety systems such as crew alerting, enhanced ground proximity warning, terrain awareness warning and traffic collision alerting.
EXTERNAL CAMERA
An additional feature on Honeywell's AW139 is an external camera to help pilots verify false or real engine fire warnings, alerts that are notoriously spurious in helicopters. While operators often use mirrors on the pilots' door pillars, Honeywell has provided an external, low drag camera which shows the engines' exhausts. In addition to revealing whether there is an actual fire, the camera will also show the tail rotor and the aircraft belly and can be swivelled to show the state of the undercarriage.
The medium-twin helicopter also has integrated maintenance/equipment and systems diagnostics, trend and exceedence monitoring and a caution advisory system in the cockpit that also records many parameters that the technicians can download.
My pilot for two demonstration flights was Marc Lajeunesse, a senior Honeywell development pilot, both fixed- and rotary-wing qualified. The day was sunny but cold as we got on board, Lajeunesse in the right-hand seat, me in the left, both of us with complete dual controls and dual system displays.
We each had one primary flight display and a multifunction display, all on 12.8in (32.5cm) liquid crystal displays, plus a larger 13.1in Sagem-built moving map display in the centre. There is an LCD "scratch pad" at each pilot's location to bring up or design whatever is required, for example, weather radar, moving map, flight plan.
Several safety features have been incorporated throughout, especially with the flight management systems. Included are limits on critical control functions, such as the trim actuators, and voting on independent attitude and heading reference system (AHRS) inputs to eliminate a rogue attitude or rate measurement - that is, voting compares AHRS1 and 2 with the standby attitude indicator and votes out the one in disagreement.
If one of two automatic flight control systems (AFCS) fails, there is no degradation of aircraft handling as the other system will automatically provide full capability. The only restrictions when that happens are a reduced never exceed speed of 140kt (260km/h) and limited climb speed and rate of 100kt and 1,000ft/min (5.08m/s).
UPDATE ON THE WAY
Even though Epic is state of the art, development is under way at Honeywell to increase its capabilities further with a phase 5 update that will include an automatic fly-away from hover. Epic has plenty of spare redundancy to incorporate such additional capabilities and there is also space to incorporate additional customer requirements, says Honeywell.
Any fixed-wing pilot conversant with modern aircraft will easily be able to use and interpret Epic since he/she will recognise similar features. However, for helicopter pilots with no experience of inputting demands to flight computers and interpreting the results, there is a four-week course given at the two Agusta/RotorSim/CAE training centres, one in Italy, the other in the USA.
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As an additional safeguard, if the pilot requests something unusual, say, of the navigation system, the display will question the input and give the pilot the opportunity to rethink. This was demonstrated in the flight.
Honeywell provides a compact disc with the cockpit presentations that a trainee can play to interact with input systems and displays. This facility has been contracted through AeroSim Technologies to instruct pilots in programming the flight management system and operating the AFCS/autopilot. It is considered that after successfully completing the full course, any instrument-rated helicopter pilot should be able to operate Primus Epic single pilot in instrument flight rule conditions.
Another interesting feature of Primus Epic is the charts and maps display. There have been a couple of recent fatal airline accidents when pilots have used the wrong runway. If requested by AgustaWestland, Epic can provide a map of the airport and a green presentation of own-ship position on the airport with the active runway highlighted. An additional upgrade can also show the profile of the flight plan take-off and landing with the terrain beneath, so there should be no excuse for controlled-flight into terrain accidents.
For SAR, the aircraft can be set up for a quick departure, as quick as one minute, says Honeywell. This includes aircraft checks completed, external power connected, flight management system initialised and flight plan and performance data competed, a remarkable achievement with such sophisticated systems. When the author was flying SAR on the northern North Sea, our quickest departure after all the above was completed was 2min.
SIMPLE FLIGHT PLAN
For our flight, a simple flight plan was loaded and displayed on the primary flight displays (PFD) and centre moving map display. For a rapid departure for SAR any search plan can be loaded and then modified once airborne to the actual location. Phase 5 will provide a choice of search patterns.
The system displays the actual take-off weight and density altitude, among other data. Our weight was 6,095kg (13,409lb) against the maximum of 6,400kg. Helicopter pilots are renowned for not knowing their density altitude and suddenly finding that they have run out of tail rotor control or engine power because although the altimeter shows a workable altitude, the main and tail rotor and engines are experiencing much higher altitudes.
Lajeunesse designed a flight around the local area and brought it up on my screen. It was easy to interpret and, as I found out, easy to fly. The secret of sophistication is pilot friendliness. This system complies and even asks the pilot if the information he is inputting is what he wants/intends when it is changed. Selecting the aids and frequencies that we intended to use was simple. A flexible design allowed me to switch selections around easily to provide the latest to be used. We then selected 2,500ft (760m) as our after take-off altitude. The radio altimeter (radalt) alert height was selected. The presentation showed the level of the ground below.
Agusta requires the cyclic stick to be central for taxiing and other ground operations so Honeywell has produced a small stick position symbol on the displays. While the aircraft is on the ground, none of the sophisticated flight-control or management systems are operative.
FLOCK OF BIRDS
The pilot rules. I came to a hover with all the stabilisation and flight director systems on line and released all the controls. The hover was accurate and the AW139 dipped and swayed gently with the wind to keep us over the selected spot. I used the coolie hats on the cyclic stick and collective lever to move us around, watching the small relative wind direction and speed indicator on the display. The AFCS is designed so that the pilot can fly through the autopilot. For example, to avoid a flock of birds ahead, he can come on to the controls to swing the aircraft out of the way and release the controls. The aircraft will then return to its original coupled parameters.
This could all be done hands off, just using the coolie hats and the heading rotary switch to direct the flight, for example, to change the speed, altitude, rate of climb/descent or heading. I transitioned into forward flight, following the flight director cues on the PFD and also the lever position that the system required as we climbed up to our assigned altitude. There is no need to use the pedals in a turn unless it goes out of balance, in which case a slight touch on the pedals is required to correct, as indicated on the small split triangle at the top of the PFD. All the information I needed to see our position in space and where we intended to go was neatly presented - attitude, heading, speed, altitude, radalt, rate of climb and descent, power, rotor RPM and our track to the next waypoint.
As we approached the pre-selected altitude of 2,500ft, there was a gentle audio alert. TCAS then suddenly alerted us to another aircraft, both aurally and on the PFD. Lajeunesse selected an instrument approach to the practice airport based on GPS and the flight management system long-range navigation. The display showed us everything we needed to know, such as our speed, the top of climb and top of the descent points, where they were, where we were, how far to go to them and time of arrival. I flew the vectored approach manually to finals using the flight director. The presentation is easy to interpret and also has a small presentation of the required collective lever position - if too low, it indicates raising it, if too high, it indicates lowering.
After Lajeunesse had selected autopilot, I released the controls. The aircraft decelerated at the appropriate point and started down. The presentation on our displays, superimposed on the PFD were identical to that of an instrument landing system approach in that we could see at a glance where we were on the glideslope and localiser. Lajeunesse set up a go-around altitude of 2,500ft while autopilot automatically uses 90kt and a rate of climb of 1,000ft/min for the manoeuvre. The AW139 settled down to a very stabilised, hands off approach. At decision height, which was announced, Lajeunesse pressed the "GA" (go around) button on the lever. The power came on, the rate of descent stopped. We immediately went uphill and gently accelerated to 90kt at a rate of climb of 1,000ft/min, after which the aircraft settled accurately at 2,500ft and joined the hold.
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On the downwind leg of the hold, Lajeunesse programmed the navigation system to perform an ILS approach onto the reciprocal runway with a decision height of 250ft. Epic first queried if we really wanted to leave the hold. We were banging along at 140kt, but at the deceleration point, we were alerted that the deceleration had been captured. The fully coupled system flew an accurate, stable, decelerating approach to the runway. The hover mode button was pressed at 60kt. Descending below the pre-selected decision height brought stern warnings "Don't sink! Don't sink!" and "Altitude! Altitude!"
IMPRESSIVE HOVER
The Epic's auto hover capability is impressive. The lowest auto hover height is 10ft (if you still cannot see the ground at this height, you have had a really bad day). The pilot can change the hover height using the up/down facility on the stick coolie hat, with a small magenta doughnut symbol on a stalk on the PFD showing the target. Another, cyan, shows the helicopter. The system will constantly operate to match the two. The pilot can move the target or change the heading and height using the coolie hats on the stick and lever.
If the target moves, the helicopter will move with it. If the target is, say, a moving vessel, the helicopter can follow the vessel accurately. The autohover capability and wind speed matches the flight manual maximum sideways limit of 45kt. The aircraft will hold a very accurate hover height even over rough seas using the radar altimeter, unlike the Doppler systems of the earlier SAR aircraft I had flown on the North Sea. In the case of a winch operation, the winch operator is given about 5% authority to remotely control the aircraft over the casualty.
I took over manual control of the hover as Lajeunesse started to remove all the stability augmentation and autopilot systems, one at a time. When the first AFCS came out, we had an advisory alert. There was no change in handling characteristics and I was eventually left with a "raw" aircraft with very little degradation of hover handling capability. In forward flight, control is slightly more difficult with pilot induced oscillations being common.
However, after a little practice during my earlier test flight on a prototype AW139, I was able to fly accurately and smoothly. After more practice, I would be confident enough to carry out an approach and landing to an offshore platform in poor conditions.
Source: Flight International
