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karatecatman · Guest

www.hindu.com/2009/03/23/stories/2009032351381100.htm
Expert highlights deficiencies in Saras flight control system

Ravi Sharma
DGCA board to probe into aircraft crash

The prototype went down as its IAF crew were verifying an engine relight

Tunnel tests by NAL establish that there were shortcomings in flight control

BANGALORE: Did the National Aerospace Laboratories (NAL), the designers of the indigenous Saras light transport aircraft — a prototype of which crashed on March 6 killing its three-man Indian Air Force (IAF) crew — err in flying the aircraft?

A senior NAL official told The Hindu that an independent, but a brief review in last December of the design aspects, including the Saras’ flight control system by an aviation specialist from Germany, had brought out deficiencies in the aircraft’s existing controls and “recommended modifications, changes and further reviews to address existing problems.”

Rudder control
On the aircraft’s rudder control, the specialist had even gone as far as stating: “On one of the quadrants in the empennage of the Saras, the cable guard limits the rotation of the quadrant. By rotating the quadrant, the cable will be stretched and it causes a load increase in the cable tension and may limit deflection angle of the control surface. In addition, this changes the kinematics. This should be investigated and corrected prior [to] next flight.”

During his four-day visit, the expert had discussed with officials connected with the Saras programme, “aerodynamic issues, especially on the balanced and trim tab, control forces in the rudder control system during single engine operation, centring of the aileron control [and] loads on the flap system.”

The expert then provided NAL with an executive summary of the individual issues which were discussed, explaining that while in some areas recommendations could directly be given, in other fields more detailed investigations would have to be performed.

Official sources close to the Saras programme also told The Hindu that wind tunnel tests carried out by NAL had established that there were shortcomings in the aircraft’s flight controls.

The twin-engine prototype went down as its IAF test crew were involved in verifying for the first time on the Saras an engine relight (shutting off and restarting, in sequence the engines in mid air).

The ill-fated prototype was fitted with new Pratt and Whitney engines that were not only larger in size, demanding modifications to the aircraft’s stub wings and the strengthening of the rear fuselage, but also produced a higher thrust (1,200 shaft horsepower) compared to the engines (850 shaft horsepower) that are flying the Saras’ first prototype.

Officials tight-lipped

Though they acknowledge the German expert’s findings, NAL officials were tight-lipped on whether the highlighted design deficiencies were investigated or corrected.

All that a senior official with the programme would say was that “the report was only a first information report on the aircraft and it would be incorrect to go by the spirit of the report.” He also added that it would be incorrect to say that the prototype was not fit to fly.

NAL Director A.R. Upadhya declined to comment.

The recently constituted board of inquiry of the Directorate-General of Civil Aviation, which will look into what went wrong when the prototype crashed, will start functioning from Monday.

iflytb20 · Posted: Mon Mar 23, 2009 3:22 pm Post subject:

I shot this pic during Aero India 07. I hope she was not the same one that crashed.

HamiltonAir · Member Joined: 25 Dec 2006 Posts: 937 Location: Bangalore

Nice pic there of the saras. I think NAL built only one prototype. May she rest in peace.
_________________
HamiltonAir

iflytb20 · Posted: Mon Mar 23, 2009 7:04 pm Post subject:

I just saw some pics or Aero India 09. The Saras flying there is VT-XRM while my pic shows VT-XSD. So unless they re-registered the airplane, i think there might have been two of them flying around.

shivendrashukla · Posted: Mon Mar 23, 2009 8:10 pm Post subject:

If you read the ET article, it says that there were 2 prototypes and the second one crashed. Also the first one will be modified into a prototype III.

Cheers
Shivendra