Demise of HF-24 Marut – Was lack of engines the real cause?

Introduction

 

HF-24 ‘Marut’ was independent India’s first attempt at creating a supersonic fighter aircraft and ushering self reliance in the critical field of fighter aircraft aviation. The country did invest considerable resources into the project and went to the extent of inviting the acclaimed German airplane designer of World War-2 fame, Professor Kurt Tank to design such a fighter aircraft. He had designed iconic fighter like the Fw 190, the back-bone of German Air Force or Luftwaffe for most of World War 2.

New Design?

It is widely believed that HF-24 ‘Marut’ was designed by Kurt Tank on invitation of the Government of India. However, my research shows that this was not the case.

Here are some key points which highlight that Marut was not a new design as per IAF’s requirement.

  • HF-24 design is actually IA 43 Pulqui III – conceived by Kurt Tank when he was in Argentina. It never left drawing board. Below picture is an art work which shows Pulqui III in different Argentine colors
IAe 43 Pulqui III
  • It was to be follow-on supersonic fighter for IAe 33 Pulqui II which was again designed by him and which entered service with Argentine Air Force.
  • This comment from the highly respected Gp Capt Kapil Bhargava always intrigued me: “the main concept of the aircraft was finalized by Tank perhaps even before his arrival in India”. +AVM SN Roy Choudhary (who set up GTRE and did some phenomenal work there) in his book also questions the HF-24 design’s ability to go supersonic even if right engine was to become available.
  • It seems IAF’s ASR at the time was wrapped around what Kurt Tank was offering rather than HF-24 being a de novo design.
  • Computerized image of the IAe 43 “Pulqui” which was never made in Argentina:
  • Only known wind-tunnel model of IA 43 Pulqui III. Description from a different site (but same model): although it did not manage to fly in Argentina, the IA 43 Pulqui III survives in this model of wind tunnel that is conserved in CEASO offices.

But was engine the only problem?

In spite of considerable effort, HF-24 Marut could not meet the Air Staff Requirement (ASR) parameters. And the biggest reason for that was lack of suitable engines. Professor Kurt Tank had designed the aircraft around an engine being developed by Bristol Siddeley of UK. However, Bristol Siddeley never managed to develop the engine due to some decisions made in that nation and Bristol Siddeley lost the economic reason to pursue further development. However, Bristol Siddeley did approach Indian government to fund the development. The story goes that they were asking for a very steep price and Indian government refused to fund the same. 

In hindsight, that proved to be much more costly decision than whatever money they were asking. Reason being, HF-24 ‘Marut’ never reached its optimal performance and instead, was flown with Bristol Siddeley B.Or. 703 engines, the same ones on Folland Gnat. 

Still, 140+ Marut were manufactured and all of them served with three operational squadrons of the IAF. Tragedy was that an aircraft meant as high altitude, high speed interceptor, was employed in ground attack role!

And in less than two decades, HF-24 ‘Marut’ was phased out of IAF, never having achieved its potential.

Popular perception says that it was lack of interest by IAF which led to the early demise of the fighter. That it did not support the program enough. Reality speaks otherwise.

However, there is one more angle to the story – and that is the role of Professor Kurt Tank and design team at HAL in scuttling a reheat or after-burning project at GTRE. A project, if it would’ve reached its logical conclusion, would’ve made HF-24 much more powerful aircraft. And allowed it to meet a high percentage of its expected requirement.

As for now, I produce excerpts from autobiography of Air Vice Marshal SN Roy Chowdhury. These excerpts tell you about the little know efforts made by GTRE to power HF-24 with a reheat engine and how, the obstinacy of Professor Kurt Tank and Indian members of design team at HAL, prevented this venture from reaching its logical conclusion

Before I proceed, I’m attaching pics of tail pipes of HF-24 MK1 and HF-24 Mk1R (this prototype flew with reheat engines). The excerpts linked below refer to this aspect of design repeatedly and are central to understand the issue which prevented evolution of HF-24 Mk1R into a true-blue after-burning fighter aircraft.

Tail section – HF-24 Mk1

Tail section – HF-24 Mk1R

The above aircraft, BD-884, is the first prototype to fly with reheat engines and underwent trials from 1966-1970.

Excerpt

Following pages have been taken from a book by AVM SN Roy Chowdhury. And show how the resistance to design change on part of Kurt Tank and HAL was responsible for HF-24 Marut not flying with indigenously modified engines with reheat/afterburner capability.

 

There are multiple urban legends associated with premature demise of HF-24 as a fighter aircraft and a platform for further evolution. One of which pertains to lack of interest by the IAF, and its desire to import a foreign aircraft. As the material shared above shows, there is more to the Marut story than these urban legends. And a honest, and clinical assessment is required to understand the structural issues, so that we don’t repeat the same mistakes.

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