Born to spy

Production

The prototype D-450 development aircraft flew on 24 June 1987, piloted by Einar Enevoldson. To prove its high altitude capabilities he set a class world record of 53,573.96ft (16,329.35m) on 1 September 1988. Two pre-production aircraft known as the D-500 Egrett II followed in 1989 and 1990, as the design edged towards certification, which came on 13 September 1991.

The aircraft was built to be foolproof, according to Enevoldson, a retired US Air Force pilot, who trained with the Boscombe Down based Empire Test Pilot School before joining NASA Dryden. After retiring from NASA, Enevoldson helped Grob with the design of the Egrett. He wanted an aircraft that was easy to fly, could take off in all weather, climb to 50,000ft, loiter in a race track for eight hours and then land in 20 minutes.

E-Systems owned the first example, fitted with various sensor packages, and Grob flew the second, renaming it Strato 1 to market the design to civil authorities as a resource management platform.

Following the end of the Cold War in 1990 and the unification of East and West Germany, the Luftwaffe cut its defence spending and the Egrett was cancelled. E-Systems pulled out of the project in 1993. Analysts had estimated the contract would have brought in between $600m and $1bn for E-Systems through the end of the decade.

By then five single-seat aircraft had been built, the D-450 (10001N14ES and D-FGEI) being a proof-of-concept aircraft. Unfortunately, it was scrapped in the wake of the decision to stop the order but the remaining four singleseaters and the only dual-seat aircraft are still flying. The second (10002 D-FGEE to N4510) and third aircraft (10003 was operated by E-Systems as N27ES but is now N520EG) are with Airborne Resources Inc from Midlothian, Texas, the fourth (10004 – N520DM) is with Bear Defence based in Tampa, Florida, and the fifth (10005 – D-FGRO, now D-FAHH) is still flown by H3Grob, as is the G 520T (10200 – D-FHHH) twin-seat aircraft. 

High-flying glider tug ​

As part of the Airbus Perlan II experiment Airborne Resources Inc’s Arne Vasenden used his Grob 520 N5410 for the highest-ever known glider tow. Perlan II is a pressurised, two-place, space capsule with glider wings designed to use only the power of stratospheric mountain waves to fly as high as 90,000ft.”

The aircraft pulled the Airbus Perlan II from 20 August to 12 September 2018 into the skies over Patagonia, Argentina. Basically, Arne gave the Perlan II a ‘leg-up’ to the stratosphere without the glider pilots toiling for hours to get up there. After the first test flight when Vasendan took the aircraft up to just 11,000ft, to check out conditions and the new towing system customised for the G 520, the next eight went up to 40,000ft or above. During the last mission on 12 September, Vasenden took the G 520 up as high as 45,100ft, where it released the Perlan II which then climbed another 20,000ft up to 65,000ft before returning to Earth. It is probably appropriate here to mention that the Perlan project team was awarded a bronze medal by the Royal Aeronautical Society on 26 November 2018 in recognition for ‘its notable contribution to the advancement of aerospace’.

New generation modifications​

The dual-seat G 520T D-FHHH is involved in payload trials and is playing a part in the aircraft’s continued evolution. The grey area below the black line is a modular payload compartment which can be detached from the aircraft. Alan Warnes

While the 1478hp Garrett TPE331-14F (flat rated to 750 SHP) is the aircraft’s current power plant, in the new generation G 520NG it would be replaced by the modern Pratt & Whitney PT-6 turboprop. It does not have the fuel benefits of the Garrett engine and only has a ceiling of 45,000ft but Tom explains why this is preferred: “We listen to our customers and the engine is a big price point for this aircraft. The original TPE331 could get you up to 50,000ft to look 250 miles beyond line of sight (BLOS), whereas the cheaper PT-6 will only fly you up to 45,000ft but you are still seeing 235 miles.” He added: “For every 5,000ft you climb, you gain 15nm of BLOS but is that worth the cost of a pressure suit and the necessary life support equipment? Our potential customers don’t think so and most don’t have the equipment to see that far anyway.”

H3Grob has modified the Grob 520T with a total-authority autopilot, thus converting it into an optionally piloted vehicle (OPV), with a side-stick installed in the rear cockpit for the first flights to control the autopilot. With Tom sitting in the aircraft as the pilot in control, the 520T was flown by an operator in the ground station or via the flight management system flight plan. Around 50hr of flight-testing has been completed so far.

The OPV gives you the option to fly the aircraft in controlled airspace with a rated pilot and, when you are in a ‘war zone’, you take the pilot out and control it from the ground

The single-seater Grob 520NG (10005 /D-FAHH) has been upgraded with a Garmin 600 digital glass cockpit and there are plans to modify the dual seater with a new GenesyS system. The optional operator console in the rear cockpit can offer two large, high resolution 23” touch screen displays, plus two foldable 12” side displays. The sensor operator can conveniently work with a full keyboard, hand controller units and a camera grip. The rear cockpit could be alternatively configured in a dual role mode for platform training or multi-pilot missions.

On the G 520NG Tom said, “We have a lead in time of 18 months to build an aircraft and we already have a mock-up built by tools we have, to verify the mould. We are optimistic that it will go into production.” But why would a customer opt for a Grob 520NG rather than say, a Global Hawk? “We are basically a lot cheaper than a Global Hawk, which costs around $280m without the sensor package, plus 20 guys to operate it. The G 520NG with sensor suite – radar systems and datalink, would probably cost a fraction of that and the big bonus for some customers is it would be ITAR free.” Tom added, “The customer could have a 24 hour persistent surveillance with three aircraft flying eight hour turns – one operating with the U-Bay sensor load, replaced by a second with a similar configuration while the third is being fitted with first aircraft’s U-Bay load.”

There is still a lot of life left in this design, 33 years after the first aircraft made its first flight. Today’s Grob 520NG could easily fulfil the ISR needs of air forces not blessed with a massive budget and secondly its non-ITAR. More countries, particularly in the Middle East, are now leaning towards nonUS-produced systems in order to get around the burdensome restrictions imposed by the US.