If hit, chances of both engines in a TWINENGINE FIGHTER getting knocked out simultaneously may not exactly be half that of one engine, but would certainly be much lower. Plus, stealth and multi-role capability demand space to store weapons internally.

Unarguably, jet engines have never been safer or more reliable than they are today. It could also be asserted that the assurance level is of such high order, it matters little whether a fighter has a single engine or two so long as the machine can deliver the desired performance and fulfil other defined criteria. While this line of argument is irrefutable, it is imperfect. Here’s why.

During peace time, birds have destroyed so many single engine fighters and killed pilots in vulnerable states of flight that the threat cannot be overstated. Admittedly, a bird hit has the potential of destroying a twin engine fighter also. The difference, however, is that given good training and sufficient emphasis on practice of emergency drills, with a twin machine there is a fair chance that both the pilot and the machine would be saved. On the other hand, if the only engine quits, the aircraft is almost certainly lost and the pilot killed. In maritime strike role, Indian Air Force fighters’ area of operation extends deep into the sea. They also operate regularly over vast inhospitable deserts in the Western Sector, Himalayan Mountains and thick primary forests. Loss of engine on a jet that’s equipped with just one would certainly translate to loss of an expensive aircraft. Worse, if search and rescue operations fail to perform optimally due to bad weather, forest canopy, loss of communication or any other reason, an indispensable pilot may also be lost. Single engine reliability cannot be a sufficient argument against such an eventuality.

A relevant case in point is the US Air Force experience. In FY2007, of the 13 F-16 Class A mishaps (meaning loss of aircraft or damage of more than $1 million; Rs 4.8 crore), as many as six occurred due to engine problems. In 2001, F-16 suffered Class A accident rate of 3.85 per 100,000 hours because of a rash of engine failures. A January-February 2008 report in Flying Safety journal also states that in most years, engine failures on F-16 cause more accidents than any other single factor. Another Congressional Research Service report to Congress submitted on April 13, 2006, reveals that between FY 1990 and FY 2004, the single-engine F-16 suffered 80 Class A engine-related mishaps for a rate of 1.31 per 100,000 flight hours. During the same period, the twin-engine F-15 suffered 21 engine related Class A mishaps for a rate of .64 per 100,000 flight hours. Therefore, both propositions—of near perfect reliability of modern jet engines as well as survivability rates of single and twin engine fighters being comparable—are myths.

What is true during peace time is even more so during hostilities. In any given battlefield conflict, chances of two engines getting knocked out simultaneously may not exactly be half that of one engine, but would certainly be much lower. Left with one of the two engines, the aircraft may not be any good for the mission, but its chances of at least limping back to home base remain excellent. With a single engine machine, the outcome is not likely to be so favourable.

Further, evolution of fusion systems to integrate data from a variety of surveillance platforms and data links to integrate all weapon systems into a networked array to defeat multiple threats have given birth to the concept of ‘air dominance’. Persistence being key criterion for an ‘air dominance fighter’, an air defence interceptor is, therefore, typically required to carry more fuel and weapons. The larger airframe required to fulfill these requirements automatically puts it in a higher weight class. The platform’s large surface area also affords room for a large number of air-to-surface weapons—thus creating a truly capable multirole aircraft. To extract optimum performance out of such an aircraft, a twin-engine configuration with adequate thrust becomes necessary.

With 4,200 accumulated flying hours, mostly on assorted types of fighters, the author’s illustrious career in the IAF comprised extensive tenure in the Jaguar strike aircraft bases as Chief Operations Officer, in-charge flying and overall base commander, which afforded him great insight into twin-engine aircraft operations. He superannuated from the IAF in the post of AOC-in-C, Southern Air Command.