Sir - I am puzzled by two articles on Grob aircraft. One, on the GF200 "pusher" aircraft, ("Novel design", Flight International, 15-21 November, P34) describes a "radical design concept". The design is not innovative, however. I believe that it draws from the tail-cone-mounted turboprop Lear Fan business jet of several years ago. The Lear Fan, also constructed largely of composites, was different in that it had three stabilisers radially oriented, instead of the T-mounted arrangement of the Grob machine. Neither did the Lear Fan have a laminar-flow wing, but the resemblance, nevertheless, is startling.
The second article refers to the "unique" Grob Strato 2C high-altitude research vehicle ("High and dry", Flight International, 31 January-6 February, P66).
This aircraft is remarkably similar to the remotely piloted US Defense Advanced Research Project Agency/Boeing-built Condor reconnaissance aircraft. The article claims that the Strato 2C has the largest all-composite (56.5m) wingspan, but the all-composite Condor has a wingspan of about 61m.
The claimed piston-engine altitude record of 60,700ft is not a piston-engine record. The Condor, with a similar twin Teledyne Continental two-stage turbocharger piston engine, reached an altitude of 67,028ft in 1989.
ALLAN PATCH
Kent, Washington, USA
Grob's unique Strato 2C is similar in design to the Condor
Source: Flight International