When a young naval instructor and his pupil — a flight cadet from Indian Air Force — marched across the tarmac to their aircraft on 21st Nov 2002, little did they know they would be ‘walking the wing’ a few minutes later. In Air Force Academy, an important tally is squared off at the end of a normal training shift — the number of takeoffs must equal number of landings. It was not to be for this crew.
The aircraft they were planned to fly that day was Hindustan Aeronautics Limited’s HPT-32 (Hindustan Piston Trainer), also called Deepak (‘lamp’ in Hindi) — a basic trainer aircraft (BTA) with side by side seating, powered by a single Lycoming AEO-540-D4B5 piston engine. The HPT-32 first flew in 1977 and was inducted into the IAF to replace the HT-2, another basic trainer from HAL’s stable.
Engine emergency in climbout
The takeoff was uneventful. The HPT-32 is a slow climber and their allotted sector was still miles away. In a climbing turn to the desired radial, at a height of about 3000 feet (altitude about 4500 feet above sea level), a sudden squirt of oil from the engine splashed onto the windscreen. It can get cold at that altitude in the local flying area of Air Force Academy (AFA) in the southern state of Andhra Pradesh (now Telangana), India. The splashed oil quickly congealed on the windscreen, severely restricting forward visibility. It was no longer “ops normal” — the instructor-pilot was facing a potential engine emergency with an ab-initio flying trainee.
This was 2002. Even in its heydays, the HPT-32 had bare enough avionics to fly. There was no navigation aid; no GPS; not even an automatic direction finder (ADF). The qualified flying instructor (QFI) from Indian Navy instinctively turned towards base and asked AFA radar for ‘vectors’, hoping to make it back before the situation turned worse. The aircraft had other plans. Oil pressure started to drop, while another big splash of oil hit the canopy and windscreen, reducing forward visibility to near zero. Vibrations started rising — tell-tale signs of a reciprocating engine fast running out of lubrication & gasping to stay alive. Within seconds, engine parameters started winding down and the aircraft began to lose height, emitting small puffs of smoke. The pilot recalls seeing “licks of flame” coming out of the main instrument panel into the cockpit. He quickly shut down the engine using mixture lever. The one-way ride to ground — about 2500 feet below — had begun!
Only option — Bailout!
Now, all pilots in basic training are taught how to fly a ‘practice force landing’ (PFL) pattern — cutting engine to idle power and trading height for speed and glide distance. A quick calculation revealed they won’t make it to the AFA runway with the steep glide ratio of the HPT-32. Force landing in an opportune field was also ruled out due to zero external visibility, leaving them with the only option — bail out!
Having completed a basic para jumping course in late 80s, I can vouch for gravitas of the decision staring the captain in the face. Out of a 3-week course we completed at Parachute Training School (PTS) Agra, almost two weeks were devoted to rigorous physical training & ground drills to prepare us for ‘static-line’ jumps (parachutes auto-deployed by a static line). Only then were we allowed to even board an aeroplane. The Deepak crew, in contrast, had none of that for what was to be a ‘freefall‘ jump. A mock drill of egressing cockpit in a static aircraft, walking the wing and jumping four feet to the tarmac was all the ‘escape training’ they had. The captain had completed a parasailing adventure camp few years ago. He recalled a small lesson on steering a parasail that would come in handy during the last few feet of parachute descent that day.
Steep glide angle; no ejection seats
The nose-heavy HPT designed to specifications from the 70s could ill-afford ejection seats (uncommon on piston-engine basic trainers even today). The later part of HPT’s service life was plagued with engine and fuel supply problems that led to many engine failures. The manufacturer HAL made many attempts to rectify issues that plagued the fleet, even proposing a parachute-assisted ‘ballistic recovery system (BRS) for the Deepak that never saw light of day (possibly because of structural issues). The services paid the cost in lives for dithering in the face of mounting pilot training requirements against a depleted fleet of basic trainers.
Bailout — a crucial decision with no time to spare
The decision to leave the familiar environment of cockpit into the unknown is decidedly tough, as attested by the protagonist of this story. But it is a decision that brooks no delay. A light plane with good “lift to drag ratio” (L/D ratio) can be force landed on a short, even unprepared field. Not so for HPT-32 that in the words of an IAF instructor had “gliding characteristics of a brick”. The nose-heavy HPT-32 with fixed landing gear was hardly a glider’s delight, as recounted by many pilots who have logged time on this aircraft. Precise statistics of bailouts from the HPT are not available in open domain; but veterans recall at least two, of which, this story remains a copybook example.
Lives were often lost when crew chose force landing over bailout (for myriad reasons; avoiding ground fatalities while flying over populated areas being one) on an aircraft that glided but very steeply .
Ejection seats were commercially available when the HPT was designed but the aircraft was not equipped with them (neither did the IAF specs call for it). HAL’s HJT-16 ‘Kiran’ jet trainer I flew in AFA ten years before this accident had ejection seats which saved many lives. In the academy, planning and preparation for ejection (HJT) / bailout (HPT) was a daily exercise. The ejection sequence, for instance, was so ‘drilled’ into us that three decades later, I can still rattle out actions if someone doused me with a cold tub of water in my sleep. Bailout, in contrast, had imponderables one could never be fully prepared for. The saving grace was ‘best practices’ handed down from one generation of aviators to the next.
The bailout procedure
IAF veteran, test pilot and A2 QFI Air Cmde Ashutosh Lal (Retd) had this to say about the HPT-32 bailout process:
“The bailout option, for some strange reason, was to be employed during non-recovery from spin. HPT-32’s post-stall behaviour was quite violent. We would often execute flick rolls and stalls at more than 1 ‘g’ — a very violent manoeuvre. But with the HPT’s steep nose-down attitude, I think, the helix angle was so much nose-down that the entire thought, training and mental conditioning of cadets and instructors was for bailing out in the event of non-recovery from spin. When you practice bailout on ground, it’s a fictitious attitude of aircraft under 1 ‘g’ condition (g = acceleration due to gravity). In gyration, ‘g’ is variable, and I used to show instructors during spin that it is possible to rise through the ‘g forces’, step on windshield coaming, and push yourself clear for a leap of faith.”
Arguably a tough act to follow at ab-initio stage! Yet the pilots in this story took the ‘leap of faith’, albeit in a slow descent. The naval QFI recounts:
“Bailout drill on the HPT-32 was practiced regularly on ground with the engine running. The pupil was told to simulate the drill by unstrapping seat harness, stepping onto the wing with his parachute strapped-on, and jumping onto the ground. The engine was kept running to simulate airflow. This was usually done on return from a sortie, just before shut down.”
Sample this representational stunt video shared on Twitter (source unknown; it’s not the HPT-32). Please don’t try this without specialist training and equipment:
— Kaypius (@realkaypius) September 26, 2020
The final moments
Back to the story.
As the HPT-32 started its steep glide towards the earth, the crew faced their moment of truth — one where preparation, nerves of steel and flawless execution must come together even as the clock (altimeter) winds down to field elevation. The captain barked orders to “prepare for bailout”. The pupil, with hardly any flying experience, reacted with alacrity and jettisoned the canopy. “Bailout, bailout!”, ordered the instructor over the screaming blast of air. To his credit, the flight cadet followed the bailout drill to the T, unbuckled, walked the wing and dived into the cool November sky while the instructor trimmed aircraft for a slow glide. The rest of the anecdote is best heard in the naval QFI’s words:
“I gave an R/T call, released my seat harness, stepped out onto the wing with my parachute and jumped towards the trailing edge of the wing. The aircraft went into a gentle roll as I stepped onto the wing. As I was flailing in the air, I got a grip on the D-ring, counted to three (for clearing aircraft) and pulled it. Initially, nothing appeared to happen; and then, with a mighty jerk, the parachute deployed. I looked around and tried to spot my pupil’s parachute but couldn’t see it. I looked down and saw that I was heading straight towards a sugarcane field with the fully grown stakes pointing straight at me! Realising that I may get injured if I fell on them, I pulled the parachute cords to one side (*recalls his parasailing experience*) and just about cleared the field; landing on a ‘bund’ instead. Immediately, a few villagers came over. I enquired from them and was informed that my pupil has landed safely on the other side of the field. The aircraft fell on a deserted stretch of land next to a road, fortunately causing no damage to civilian lives or property. Within a short time, the SAR helicopter landed in a field next to us and we were airlifted to the academy”.
HPT’s history — Missed opportunities or delayed decisions?
Many others were not so lucky. It took at least 17 crashes and the loss of 19 pilots before IAF put out the ‘lamp’ that was HPT-32 ‘Deepak’. This included flight cadet Deepika Sharma’s HPT-32 crash in May 2008 — the second fatal crash involving a lady IAF pilot after Flying Officer Harita Deol died in an Avro crash in 1996. The HPT-32 was finally withdrawn from service after two experienced instructors from AFA died in harness in what was to be the Deepak’s last flight (July 31, 2009 ). All basic flying training shifted to indigenous HJT-16 Kiran for a few years till the imported Pilatus PC-7 was inducted into service.
Veterans this author spoke with rued many missed opportunities in the HPT saga — including opting for a new propeller (or engine), fixing the spate of engine failures, and, in the end – the timing of decision to ground the aircraft. Like its more enduring rotary cousin Alouette III, the HPT had ‘undefined’ life and ‘on condition’ maintenance & servicing philosophy. IAF and HAL managed to ‘stretch the glide’ from first flight in 1977 to induction in 1984 and withdrawal in 2009 — a service life of 25 years versus a nominal calendar life of 30 years. The price was paid by those who lost loved ones. An industry & IAF veteran raises pertinent questions:
- The HPT had two issues that plagued it. Fixed landing gear causing excess drag, and a propeller that couldn’t be feathered. We couldn’t have addressed the former, but the latter was easy and a lot of options were available. Why was there no motivation to do so?
- Could it be that IAF/HAL lost the knack of operating/maintaining a piston-engined aircraft? Was erosion of understanding and practical knowledge of operating piston-engine airplanes — with its nuances of lean / rich mixtures, operation and maintenance procedures — a factor in the unreliability and fatalities?
HPT-32 is long gone (11 years to this date). “Too late to do a post-mortem”, the veteran sighs.
Enter Hindustan Turbo Trainer HTT-40!
HAL’s new kid on the block is HTT-40 (Hindustan Turboprop Trainer). Many lessons have been learnt and much has changed. Ejection seats, enhanced glide performance, 6-turn spins, modern avionics, reliability of key systems, and many improved features on the HTT-40 means crew may never have to ‘walk the wing’ again. As the HTT-40 is ushered-in, all stakeholders will do well to revisit past lessons with a clear, unbiased mind. The entire edifice of aviation stands on a foundation of “trust, but verify”. Often, tough design decisions are called for. Dithering almost never helps.
The trust factor
The naval QFI who successfully bailed out on 21st Nov 2002 with his pupil had this to say in the end:
“When I told him to go, my pupil didn’t hesitate and went out quickly. This is not easy and any delay on his part would have made the aircraft descend below minima and endangered my life, as I can only bailout after my pupil did (an instructor will never think of leaving the aircraft before his pupil). This reflects the implicit trust the pupil has on his instructor. It is therefore the responsibility of the instructor (and seniors in aviation) to develop knowledge, skills and behavior worthy of that trust.”
These are golden words. The terms “pupil” and ‘instructor”, the ‘bonding’, and the ‘trust factor’ that underpins this sacred relationship will now be tested on new, more modern, indigenous BTA programs where, once again, the penalty for undelivered promises and oversight will be young lives. Here’s hoping nobody pulls the handle on “trust”.
Happy landings! May your takeoffs and landings always square-off.
©KP Sanjeev Kumar, 2020. All rights reserved. I can be reached at firstname.lastname@example.org. Views are personal and do not reflect that of the service or the industry at large. Cover photo of HPT-32 from Wikimedia Commons CC BY-SA. Images from ace military aviation lensman Sanjay Simha’s collection have been used with permission. Do visit his website VelocityTTL.
Anecdotes from Air Warriors
Why was the HPT-32 not provided with ejection seats?
“The HPT had a big problem with weight. The first prototype weighed around 1400 kg and took ages to climb. The designer at HAL was under huge pressure to improve performance. They did some drastic weight reduction and reduced weight to 1200 kg which was huge (~14.3%). This without reduction in airframe ‘g’ limits. Ejection seats would have increased weight quite a bit. Also, in those days, all basic trainers worldover came with pilot parachutes.
Engine cuts and deinduction of HPT-32
“The problem was with the airframe fuel system. HAL used to come out with mods and swear the problem was cured. But ‘engine cuts’ continued to occur with monotonous regularity. Finally, in 2009, two QFIs were killed during a forced landing. IAF took a hard stand and the fleet was grounded. Another problem was cost of replacement, interruption in training and over 100 HPTs in the inventory for disposal. I don’t know where they are now or what was their ultimate fate.”
— Air Marshal Philip Rajkumar
On HT-2 & bailouts
“In Feb 1962, Flt Cadet Sidhu and his instructor Flt Lt Bishnoi bailed out of a spinning HT-2 at Jodhpur. Sidhu survived and retired as a Group Captain. Tragically, Bishnoi’s parachute was sliced by the aircraft’s wing tip and he fell to his death. We were in the Intermediate stage and all of us were shaken by the tragedy.
Another crazy incident took place with my coursemate Sadhu Singh Gill. He was in the rear seat of a HT-2 at AFS, Bidar. He was trying to demonstrate a stall turn and hammer-stalled instead. His canopy slid forward, harness cable broke, and he was catapulted out of the aircraft. With great presence of mind, he pulled the ripcord and the canopy opened just in time to cushion his landing. His pupil landed the aircraft. Fact is sometimes stranger than fiction!”
— Air Marshal Philip Rajkumar
“Solo sortie. As usual…(I was) steep on base leg. Turned final, engine failed. Continued approach (this was the only option!). Switched off on runway, did quick egress and came out. Fuel was gushing from front cowl like an open tap! Had lemon juice on runway provided by ambulance!
Decades back…(I was) returning from sector after countless manoeuvres and spins. Instructor told me “you need to screw this machine to extract performance”! On downwind, the engine failed! We tried relight — no joy. Flaps up, cut corner – happy landings again! Instructor asked me – “Did you surge the engine?”
— a young air warrior who did not want to be named.
When ‘threat’ of bailout was used as an effective teaching tool for aerobatics!
“There was this keen cadet who was hell-bent on flying fighters. In spite of his airsickness, which continued till MTT (mid-term test), he was struggling to do barrel rolls to left. Even the templated ‘mechanical approach’ was not working out with him!”
“As an involved instructor-pupil duo we were at it. Suddenly, out of frustration, I said – brother, this is not right. I am putting in so much effort and you are not fighting your fears. Here, you take the aircraft — I am bailing out! You go back and tell them my instructor bailed out at Phulpur!” (near BFTS, Allahabad).
“I opened my 5-point harness. The speeds were lesser than 150 kmph; throttle was idle; slipstream was minimal. I opened the canopy — without letting go the canopy — mindful of the fact that it might just fly off under the trapped dynamic pressure!”
“My pupil screamed and said, “No Sir, no Sir! I will do it!”. His fervent pitch carried over the din of intercom and slipstream!”
“Needless to say, as we climbed in silence, i put on my harness, silently rechecked the canopy, and retrimmed the ac at 200 kmph. My pupil resolved it all and, boy o boy! – the barrels that followed were copybook!”
“He went on to score very high on aeros!”
— Air Cmde Ashutosh Lal (Retd)