Czech aircraft manufacturer, Aero Vodochody has successfully completed the fuselage strength test of the Aero L-39NG advanced jet trainer and light attack aircraft.
The tests were performed on the L-39NG prototype with serial number 7002 at the Czech Aerospace Research Centre (VZLU). This is an important milestone on the road to full certification of the aircraft.
The purpose of the tests was to verify the strength of the airframe according to the requirements of the European military regulation EMACC (European Military Airworthiness Certification Criteria). During previous tests, the fuselage was loaded by bending, by inertial forces of the engine and also by forces from the horizontal tail. The last realized test represented the most critical case, with the combined bending load of the horizontal and vertical tail.
In this test, the aircraft fuselage was loaded to the limit load at first, corresponding to the maximal possible aircraft load in flight, where no permanent deformation of the fuselage has been noted. Subsequent load to ultimate load (150% of the limit load) was performed and the fuselage was intentionally loaded with higher forces leading to a structural failure that occurred at 110% of the ultimate load. The difference between the ultimate load and the limit load represents in aviation worldwide the standard safety factor of 1.5.
David Novotný from VZLU notes: “The intention of the test was to withstand the load corresponding to the maximal ultimate load. This proved the strength of the structure. During the test we have reached 110% of the ultimate load, then a deformation appeared, which disallowed further continuation without the risk of destroying the fuselage. At the same time, we have achieved the necessary failure mode and the structure proved the appropriate reserve for future aircraft development. Therefore the test was successful.”
The path of the second prototype in VZLU is not finished yet with the fuselage number 7002 to undergo further tests.
“We will continue with pilot seat hinge tests and the test of engine bed in the forward direction, which is actually an emergency case,” adds David Novotný.
“Now we have a campaign to examine the wing limit states, then we have another partial test and at the moment we are basically launching a campaign of fatigue experiments at VZLU, which is another big part of the certification process,” said Pavel Henzl from Aero Vodochody.
The L-39NG is a joint project of two private companies, the largest Czech aerospace manufacturer AERO Vodochody AEROSPACE and its strategic partner, business and military manufacturing company OMNIPOL.
The Aero L-39NG (Next Generation) is a turbofan-powered military trainer aircraft currently under development by Aero Vodochody as a successor of the Cold War-era Aero L-39 Albatros.
Designed primarily as a basic and advanced jet trainer, the L-39NG can also perform a variety of other missions including light combat, close air support (CAS), counterinsurgency and reconnaissance.
The L-39NG is a single-engine two-seater with staggered seating and advanced cockpit design that includes a full glass cockpit, a sophisticated onboard virtual training system, and a Helmet Mounted Display (HMD). The aircraft is equipped with five hard-points for weapons for light attack missions.
The aircraft is being developed in two stages. While the L-39NG Stage 1 is an upgrade of the original L-39 airframe with a new engine (Williams FJ44-4M turbofan) and avionics, Stage 2 is a newly built aircraft with several design improvements such as the wet wing without the type’s distinctive wingtip fuel tanks.