Control checks – not normally an airborne requirement

“Diamond Black check in.” I called for the radio check for my wingman to check in after we had started and done our pre taxi drills.

“Black Two,” Ike replied. He was a most reliable No. 2 – always there with sharp eyes and a ready sense of humour.

“Roger, channel Alpha One go.” And I called for taxi clearance prior to our training mission of fighter pairs. That started a sequence of events as we taxied out for Runway 30 at the RAAF fighter base at Williamtown NSW (Australia).

We had been training hard over the last couple of months. The political scene with our northern neighbours was described in intelligence reports as “volatile.” As a result, our training was focused on “real war” scenarios with much live firing of rockets, 30 mm cannon and practice dive bombing missions.

While these were done on the Bombing Range at the RAAF’s Saltash facility near Williamtown, we had worked up to flying high-low and low-level missions with the requirement of weapon impact within plus or minus 15 seconds.

But now the focus had changed. And we were tasked to concentrate on ACM’s – air combat manoeuvres.

These were to address high-level interdiction missions thought to be the most likely of roles in the not-to-distant future. This called up skills in ACM techniques, also known as dogfights.

Formation takeoff F-86s
Formation pairs takeoff were a normal operational requirement.

“Clear for Takeoff Diamond Black,” came over the radio as we rolled onto the runway.

Brakes applied, windup signal to Ike as I advanced the throttle to 7,500 RPM. Checked over my right shoulder and there was Ike’s thumbs up showing he was all ready for the formation takeoff. We rarely operated as single aircraft and when flying in a formation that was always done from the start of the takeoff until just before landing from a low-level “battle formation pitch-out.”

I acknowledged and, with a thumbs up, gave the palm chop signal as we released the brakes in unison.

Thrust slowly up to 7,850 RPM – not quite full thrust to leave a small amount for Ike to adjust his formation position.

Now airborne a nod of the head to show gear selection and get the undercarriage stowed before the speed limit of 180 knots was exceeded. The Sabre, if light, could be airborne and cleaned up with 300 knots by the end of the runway. Today, however, we were full of fuel and heavy, but still the gear speed limit was an issue we always needed to keep in mind.

The Sabre was one of the first aircraft built to have “fully powered hydraulic irreversible controls.” As a transonic and supersonic aircraft, control forces needed the support of hydraulic power. In some circumstances this power could cause wing twisting, particularly around .92 Mach, and a wing roll and control reversal would be encountered.

There were essentially three hydraulic systems: one engine-driven normal, an engine driven alternate system and a final back-up of an electrical driven system which could be connected direct to the aircraft’s battery should the other two fail.

Checking of these systems was required immediately after start for each flight and a “puddle down” procedure was employed as we would rapidly move the control column in a small circular motion to exhaust the normal system and check the automatic change over to the alternate system.

And that was considered an adequate check at the time, but little we realize that the check did not address the surprise I was soon to experience.

F-86 level
Clean and accelerating.

Airborne and “clean” I turned left to intercept the “190 Diversion” track as Ike slid to the inside into a wide battle formation where we would clear any threat from behind for each other and accelerated to the normal climb speed of 450 knots.

Trimming forward as we gathered speed, something felt wrong with the feel of the aircraft. I could feel a small vibration and rubbing sensation through the control column. A check of the engine instruments revealed nothing, but I decided to slow up and see if there was change.

“Diamond Black speed brakes go,” as I raised the nose and started a deceleration. Speed brakes selected out gave a 2g pitch up at high speeds and required coordinated forward movement of the control column and continuous forward trim.

As we slowed: “Speed brakes go,” as I called them in and started the reverse continuous back trim and that’s when I realized my concern was justified but not for what I was about to discover.

A wing waggle as I signalled Ike to rejoin in close echelon formation and I continued to slow down… but I had no further rear movement of the control column.

Something solid was stopping it as I pulled with both hands it would give an audible “clunk” and lock. I imagined it was like the rear stop being brought well forward and reality that was almost what had happened.

We had been trained for various emergencies in the Sabre with one being a quill shaft failure. When this happened, the only hydraulic power for the flight controls was the battery through the electric pump and the procedure was to use rudder – they were cabled – for roll and engine thrust for pitch and maybe, as a last resort, some hydraulic accumulator for the speed brakes.

Then the plan was to manoeuvre for an ejection over land as a landing would be too risky if all controls jammed late in an approach.

Black Diamond Sabres
Sabres used by the Black Diamond Aerobatic Team.

We were also well trained in airborne damage control should we have a collision or take damage from enemy fire and therefore would fly a dummy circuit at altitude slowly progressing through the required configurations.

And this is where our training came to the fore.

“Diamond Black, Check Hooks,” I called. These hooks needed reconnection to our backpack parachutes and would convert the ejection sequence from high altitude mode to low level mode. In this configuration we could eject in level flight, providing we had 200ft and 180 knots.

These days the seats offer better than a zero-zero capability but at the time the 200/180 knot was the best we had and if an ejection was required it would be a low level one not a high level one and within the “seat envelope.”

I saw Ike slide into close trail combat formation and he reported no obvious signs of leaks or any outward damage. And the aircraft was still flying nicely but with very restricted rearward control column movement.

To maintain control, I had slowed to 180 knots and did not want to go slower until I had the gear down so I called “gear down” and waited for the trim change, if any, to occur.

At 170 knots, all was OK so I slowed little by little but was not game to go below 150 knots where the aircraft was still controllable and I could maintain level flight albeit with the control column against the rear obstruction.

I thought if I could fly a low, flat approach and get a touch down early enough the landing would be OK, but I needed to manage a flare as soon as I passed the threshold.

I left the gear down and reasoned that an increase in engine thrust at the flare would increase speed and cause a fly away but if I extended the speed brakes there might be enough to flare and help slow the aircraft before touch down.

I practised this “speed brake flare” but forgot to call it to Ike. I got a small round-out and speed reduction but it caught Ike unawares and he overshot me low and to the right.

But it’s the team that is always there and his first response was to ask if I was OK.

“Sorry, Ike. I’m fine. I’ll turn left and you can reform. I’ll try a straight in approach. Let’s go Apha one.”

“Willy Tower, Diamond Black, declaring an emergency. Control problems and would like clearance for a long straight-in approach.”

“Diamond Black, you’re cleared as requested we have been briefed by radar and have been monitoring your transmissions. Suggest you use runway 12 as the sand dunes on 30 may present as an obstacle and it’s very flat for 12. Wind is not a factor.”

I had not thought of that and what a great idea. So we flew a wide downwind and lined up about 8-10 miles out.

I gently pressured forward on the control column to start a gentle descent and worried if the rear movement I had would not reduce but it was still OK as I came back against the stop again. Ike had moved into very close echelon now and I had only one thought: land or eject, and the commit point was 200 feet.

Again I called “Check Hooks” and it wasn’t until later I was told I had already called it, but I had no recollection, such is the effect of adrenalin and focus on the emergency I suppose.

Lower I drifted and it became hard for me to keep the runway in sight but it came into view slightly to my right as I adjusted heading. Lower now as I needed to get as low as possible without hitting the ground before the runway.

Through 200 feet and committed.

The threshold slid past and I felt high – go around or land? I closed the throttle sharply and waited.

Sabre landing
Sabre with sidewinders landing. Note speed brake extended.

The speed bled off and the Sabre started to sink – speed brake… NOW!

The flare happened and the aircraft touched down with a slight bump and skip as I heard a roar close by.

Ike was there for me to the touchdown and I saw him go around for a low level pitch out – a great sight to me at the time.

I can’t recall the touchdown speed but the aircraft had been in for brake serving immediately prior to this flight and one of my tasks was to check the brakes on landing – that I forgot about until the Flight Commander, Ray Fox, a Korean War veteran in the tower called up and said wryly, “Nicely done – at least we know the brakes work.”

It is times like this when one recalls the many friends and team mates one has worked with. It is real camaraderie and is a value that never diminishes and when things go wrong, it comes to the fore in a way that one can never forget.

The cause of the jamming was the incorrect fitment of the control column mass balance. The mass balance being provided to control the required level of “stick force per G” in manoeuvres.

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4 Comments

  • Great story, Maurie. I flew the Canadian Sabre 6 in Germany with the RCAF. I note some slight differences between our aircraft and the RAAF model; as I remember, for hydraulic power, we only had the normal system and a battery powered alternate. Our RPM gauges were in percent rather than RPM. With drop tanks, we climbed at 350 knots to .92 mach. Clean,I think we climbed at 400 knots to .92 Mach. Our “bang seat” was good to 200 feet and 90 knots in straight and level flight.

    What would you give to fly one again? (;>0)

    John

  • Nice article. It a good reminder for all pilots to practice control failure procedures!

    Well done on saving the aircraft!

  • Thank you gentlemen. I find writing these articles bring back such great memories. The RAAF Sabre did have a few differences to the F-86. The engine was a Rolls Royce Avon, Mark 20 – prone to compressor stalling -later the Mark 26 with variable inlet guide vanes. It also had a little more thrust than the USA one. We had two 30mm Aden cannons @ 600 rounds/minute replacing the six machine guns but that brought a problem and resulted in the “fuel dipper.” It seems the shock wave when firing the Aden’s would cause a compressor stall so when firing RPM was automatically reduced about 200 RPM which solved the issue. I cannot recall if this was only at high or low thrust settings. Again, thanks for your comments.

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