By
Daniel E Tyler
Copyright © 2000 Daniel E Tyler
All Rights Reserved
Dan Tyler, former C/229th pilot, writes monthly columns for Australasian "Heli-News" and AOPA magazines in his capacity as Helicopter Association of Australia (HAA) President. This article is a recent contribution to those publications and describes an in-flight engine shutdown in UH-1H "020" operated by C/229th in Vietnam July, 1970.
I’ll never forget my first simulated forced landing in a helicopter. For the first few hours of dual instruction, we hadn’t done too much air work. Most of the time had been spent trying to find the hover button.
Unlike most of my classmates, who had no previous flying experience, I’d done about a hundred hours and had a fixed-wing private licence before I started Army flight school. So I didn’t need to spend much time doing S-turns along a road or turns about a point at that particular time. I must have had about seven or eight hours dual instruction when we started on touchdown autorotations.
I learned to fly in a US Army OH-13G -- which was basically a Bell 47G. It had a 200 horsepower Franklin engine, wooden rotor blades, a -600 transmission, and a narrow bubble. Two other primary trainers were also used by the Army at that time:- the TH-55A (Hughes 269A) and the OH-23C (Hiller UH-12C).
During 1969, the US Army had cranked it’s helicopter pilot output at the Primary Flight School right up to the maximum. Primary training was at Ft Wolters, Texas - about 100 kilometres west of Ft Worth.
About 400 student pilots, consisting of commissioned officers and warrant officer candidates and a few foreign students, started rotary-wing flying training each fortnight. About 250 of them graduated twenty weeks later with a hundred hours under their belts including basic emergencies, confined areas, pinnacles, day and night cross-country navigation, and basic formation flying.
From Ft Wolters, student helicopter pilots moved on to either Ft Rucker, Alabama, or Hunter Army Airfield near Savannah, Georgia, for instrument training, UH-1 Iroquois conversion, and tactics - before getting their wings. As we moved from one stage of training to the next, we were assigned new instructors at different stage fields. But, like most pilots, I remember my first instructor best.
Homer Youngblood was a native American from the Arizona Navajo. He had been too young for Korea and too old for Vietnam -- but he’d done about 10,000 hours of civil fixed-wing crop spraying when Southern Airways Corporation offered him transition onto helicopters and a job as a primary instructor at Ft Wolters.
I was too inexperienced to know how good a helicopter pilot Homer really was - but to me he seemed like a genius. He could make that OH-13 do whatever he wanted. I had studied the theory of autorotation in ground school, and Homer discussed it again before demonstrating the first one - a straight in touchdown autorotation onto a concrete lane at one of the many stage fields around Ft Wolters.
He made it look pretty easy. Then it was my turn to try. I was so far behind the machine the first two or three times, I have no idea what happened. But after awhile I was going through the motions even though it was a bit of a blur.
After that first session, Homer warned me that from then on I could expect simulated forced landings on every training sortie. He taught me to lower the collective, check RPM, trim the helicopter, establish 40 knots, pick a spot, and then manoeuvre for a landing into wind. It sounded so simple. The first time he rolled the throttle off without warning, I froze. Homer left me in no doubt that this was the most fundamental manoeuvre in all of my training and I had better learn to get it right.
After a couple more sessions, things started to slow down for me and I could recognise the variations from different airspeeds, RPM, flare heights and glide angles -- and make the appropriate corrections at the termination of the manoeuvre. On 26 May, 1969, after 11 hours and 35 minutes of dual instruction including 15 or 20 touchdown autorotations, I soloed in a helicopter for the first time.
In primary training we did straight in and 180o autorotations, low-level straight in auto’s, and also engine failures at the hover. On virtually every dual training sortie, we were given a practice engine failure at some point.
Later, in instrument training, we learned to enter autorotation under the hood -- establishing airspeed for minimum rate of descent and turning into wind. In UH-1 transition, we added 360o and night low level autorotations to our flying skill repertoire.
There was a lot of debate about autorotational landing techniques in those days. In the early days of US Army rotary-wing aviation, a constant-attitude, no-flare technique had been the norm for power-off landings. A few years later, the Army embraced the “flare” approach.
While I was training, a report had come out which found that mis-judging flare height and failure to level the skids prior to touchdown was resulting in a lot of training accidents. The possibility of returning to the no-flare technique was discussed - although student pilots were not party to the debate.
I got my wings at the end of January, 1970, and then went on leave for a month. On 2 March, along with most of my flight school classmates, I flew out of Travis Air Base near Sacramento bound for Bien Hoa Air Base in the III Corps area of South Vietnam.
The unit I was assigned to in the 1st Cavalry Division had suffered operational losses of key personnel and was struggling to meet its direct support commitments at the time I arrived. As a result, they couldn’t spare either an aircraft or an instructor pilot (IP) to give me my “in-country check ride” before throwing me in the deep end as “peter pilot” (co-pilot) on a UH-1H.
Not only had I not practised any autorotations for six or seven weeks -- I hadn’t done any flying at all until my first combat assault mission in mid-March. Things were hot and heavy for the next few weeks and I had well over a hundred hours logged “in-country” before I was finally scheduled for my “in-country” and “90-day” check rides -- to be done concurrently.
The day before the check ride (which would have included some autorotations), the unit IP received word from the Red Cross that his father had passed away. He started packing a bag to go home. Then the commanding officer came down to his hootch and told him to pack everything, because he wouldn’t be coming back. The Army’s policy was -- if you went home on emergency leave with less than three months remaining of your tour of duty -- they didn’t bring you back.
We didn’t have any other IP’s in the unit and none were scheduled to arrive any time in the near future. So it was decided to train one of my contemporaries as the new company IP. Because he was relatively inexperienced and we were busy invading Cambodia at that time, that process took a couple months. Therefore, all unit check rides were “waived” - as was the flight time limitation of 120 hours per month. Most of us were flying about 160 hours a month at that point.
After the Cambodian Incursion, our unit was relocated to another base camp. I had been an aircraft commander for about a month and had just been selected for training as a flight leader. I had gone to Vietnam as a Warrant Officer, but the army decided I should be commissioned a 2nd Lieutenant in line with being a flight leader.
We had a couple new helicopters in the company - replacing machines lost during the previous few months. All-in-all, it was a pretty busy time and company operations had not yet had time to arrange any check-rides.
On 20 July, 1970, I was scheduled to fly “Peter-Pilot” (co-pilot) in the flight leader’s aircraft. That day was to be my last “on the job” training session with an experienced flight leader before appointment to that position in my own right.
We were flying “020", a newly-arrived machine that in an earlier life had been a “D-Model” Iroquois - but which had been completely re-built as an “H-Model” with new dynamic components and a brand new T53-L13 engine.
The aircraft commander, Captain David Stone, flew from the left seat and did most of the coordination with ground units while I flew in the command seat and coordinated with the other five helicopters in the flight and our two AH-1G HueyCobra escort gunships.
We were doing a series of insertions into an area north of Xuan Loc located along the southern end of the central highlands. The terrain was hilly and covered in triple-canopy jungle.
Just after noon we dropped a platoon of Air Cavalrymen into an LZ and were returning to Fire Support Base Mace for the second lift. I was on the controls, level at 2000 feet southbound, leading two “‘V-of-3" formations with gunships in trail.
I noticed the master caution light flicker and looked down to see the “Engine Chip” segment illuminated. I could hear a change in the engine noise. The AC was in the middle of a radio call so I waved my hand in front of his face to get his attention and pointed to the light. At that instant, the helicopter yawed, the “engine out” light came on, and the RPM started to deteriorate.
I bottomed the collective, trimmed with right pedal, glanced at the N1 in time to see it drop through 50%, and looked outside for a place to go. I heard one of the pilots struggling to stay in formation with us say, “What are you doing, Yellow-One?” Captain Stone keyed the mike and said blandly, “Flight, Yellow-One’s just had an engine failure.”
By that stage I had identified a wide bend in the Dong Ngai River as a possible forced-landing area and had started a shallow 180o turn to the right toward that spot. As I got a little bit closer, I noticed a clearing on the far side of the bend. I wasn’t sure I could make it that far, so I tightened the turn, pulled a little collective and nosed over a bit to stretch the glide. If I didn’t make that, I could go for the river, which appeared to be shallow on the inside of the bend.
At that point I remember looking back inside at the instruments. The rotor RPM was at the bottom of the “green”, N1 and N2 were at zero, and about half a dozen segments were illuminated in the caution panel. Up to that time, I had been waiting for Captain Stone to come on the controls and say “I’ve got it.” Instead, he keyed the mike and asked, “Are you okay to take it in?” I heard myself say, “Yeah, I’m fine.”
As we approached 90o in the turn, I heard “Yellow-Two” say that he and “Yellow-Three” would follow us all the way to the ground. Gunship lead called and asked if we were headed for that little clearing on the other side of the river. I replied, “Yeah, if I can stretch the glide that far.” He said, “We’ll ‘prep’ it for you.”
I looked out the right side and saw the two Cobras roll hard right and nose over - a second later I watched pair after pair of 2.75 inch rockets streaking toward the tree line around the perimeter of the clearing.
I became aware that the door gunners were struggling to jettison the ammo cans strapped to their M-60 mounts and to find the seat belts that were almost never used in Vietnam. I heard Captain Stone asking them if they were secure.
By then I knew I had the area made. I couldn’t see any obstacles in the middle of the clearing. It looked like it might have once been a rice paddy. I lowered the collective slightly and lifted the nose a bit. I could hear the rotor RPM climbing back toward the “top of the green”.
I don’t remember much about the flare but as I levelled out I saw one of the “snakes” cross in front of me low and tight - the turret-mounted mini-gun ripping leaves off the trees at the edge of the clearing only 75 metres ahead. So far so good - then came the pitch pull.
The area had looked like a putting green from 1500 feet. But as I pulled pitch at the bottom and the air flow reversed through the main rotor, the chest high elephant grass suddenly laid flat in the down wash to reveal two ugly truths.
First, I had misjudged the height of the grass and had pulled pitch too early. I was still ten feet in the air when I should have been five feet. Second, sharpened bamboo punji stakes which had been concealed by the grass were spaced throughout the clearing.
I guess I should have expected that. The bad guys used to put anti-helicopter punji stakes in what they thought were likely LZ’s. I never heard of anyone being killed by them, but they could poke a hole in the sheet metal and fuel cell and take the helicopter out of action for a couple days.
It was too late to manoeuvre and fortunately there were no stakes directly beneath me. Since we were empty and fairly light on fuel, there was enough rotor inertia to compensate for my mis-judgement. I must not have completely zeroed-out the forward speed - because when the skids sank in the mud the helicopter nosed over slightly and I watched the main rotor come within about five feet of the ground in front of me, before settling back. I was just cursing myself for my mistakes when I heard the gunship leader over the radio saying “Great job, Yellow-One!”
I looked out the right door to see “Yellow-Two” hover beside us. “Yellow-Three” was just touching down on the other side. I tried to key the mike to warn them about the punji stakes. But in that next second or so, the crew chief, Sergeant Neidlinger, ripped the pilot’s door open and dragged me out of the seat. He was a solid guy (nicknamed “Sergeant Rock”) and nearly broke my ribs doing so.
As flight leader, our ship was equipped with a top-secret KY-28 encryption/decryption device. We were warned when the KY-28 was issued - “If you don’t bring it back with you - then don’t come back yourself.” So while the crew chief and door gunner removed the M-60's, Dave Stone and I disconnected and removed the KY-28 and grabbed all the maps.
We were probably on the ground for less than 60 seconds all up. The rotor was still turning on “020" when we lifted off. Captain Stone and the gunner were on board “Yellow-Three”; Sergeant Neidlinger and I were on “Yellow-Two”. The snakes prepped our flight path with mini-gun fire as we climbed out.
As we flew toward Fire Support Base Mace, Sergeant Neidlinger kept saying “You did it!! You did it!!” He was on his third tour of ‘nam and had a couple thousand hours of combat assaults -- but that was his first engine failure.
My thoughts were of Homer Youngblood. But they were interrupted by the AC announcing that an air strike was being organised to blow up our helicopter unless we could absolutely guarantee that the KY-28 was secure. We pleaded over the radio for the air strike to be called off - telling Brigade headquarters that there was no damage to the helicopter and that all machine guns and maps were secure and that the encryption/decryption unit was sitting on my lap as we spoke.
The brass finally agreed to cancel the air strike and to organise a maintenance team to rig the machine and a Chinook to lift it out. When we landed at FSB Mace, Captain Stone commandeered another helicopter to lead the flight and a quick reaction force was organised to provide security in the LZ while “020" was rigged for hook-up. Within an hour and a half, “020" was dangling beneath a CH-47 on its way back to Bien Hoa.
I later learned that the accessory-drive gearbox had completely disintegrated. The engine had only 22 hours since new when it failed. The helicopter was given a “hard landing inspection” and a new engine and was back in action within two days. I was commissioned, officially appointed a flight leader, and permanently assigned to “020" with Sergeant Neidlinger as my regular crew chief.
After about six months in country, I finally got my “in-country” and “90-day” check rides. As I recall, I had difficulty getting the autorotation just right, but the IP decided in light of my recent experience not to press the issue.
I had another, more serious, in-flight emergency a couple months later when the hydraulic system blew a seal and we lost all the fluid overboard. That was much more exciting than the engine failure, but once again, we escaped without any further damage to the aircraft.
I also had another engine failure, but we were on the ground “hot re-fuelling” at the time. The re-fueller switched from one fuel bladder to another without us knowing about it and accidentally tapped into a bladder of water. The fuel gauge started to go crazy and the fire in the engine went out shortly after.
Still another time, a T53 engine swallowed a dzus fastener which gave us some compressor stall and high EGT - but we had plenty of power for a normal landing. By the end of my tour in Vietnam, the only airframe damage to helicopters I had been flying was a few bullet holes.
My next assignment after Vietnam didn’t involve much flying. Shortly after leaving the Army and just before moving to Australia, I got my FAA helicopter flight instructor rating on the GI Bill. That involved quite a few autorotations.
While studying at Sydney University from 1973 to 1976, I occasionally flew Kiowas with the Australian Army’s 161 Recce Squadron at Holsworthy - in my capacity as a US Army reservist. It was there that I was introduced to the idea of using two distinct pitch-pull movements in the touch down phase.
The US Army had taught autorotations using one steady pull on the collective lever. But the Australian Army technique involved an initial, fairly abrupt application of a small amount of collective to check the rate of descent while levelling the skids, followed by a smooth application of remaining collective pitch as the aircraft settled onto the ground. Major Tom Partridge, when he was OC of the Squadron and a QFI, spent some time showing me the finer points of the manoeuvre.
About 18 months after finishing law school, I was doing some casual civil flying around Sydney. I was tasked to pick up a Hughes 500C from Rex Aviation and fly to Sydney Airport to meet an ABC film crew. The ABC didn’t have their own helicopter yet (this was late ‘78 or early ‘79) but a PNG-operator had just traded the 500C for a new 500D. The used machine was available for cross-hire by commercial operators.
In response to increased fuel taxes, angry truckies had blockaded major highways around Australia - including the Hume Highway at Razorback Mountain south west of Sydney. The ABC wanted to fly down and cover the story.
I picked up the journalist, cameraman and sound man at Flight Facilities and was cleared to leave the control zone on track to Stanwell Park at 1500 feet. About a mile south of Audley Weir, I heard a bang and the machine yawed left and right a couple times. I immediately dropped the collective and looked at the instruments. N1 was high and N2/NR was a little bit low - then I noticed the TOT was about 900o. At that stage I put out a “Pan Pan” call and told Sydney Departures I had a partial power loss and was making a precautionary landing in Royal National Park.
I raised the collective a bit just to see what would happen. The NR dropped further while the TOT needle went out of sight. I lowered the collective back to regain NR and rolled the throttle off to save what, if anything, was left of the engine. The TOT dropped back to the high yellow range.
At that stage a sealed road through the park looked like my only option. I wasn’t sure it was wide enough. But then I noticed a clearing about 70 metres off the road. I didn’t know it at the time, but that clearing was actually the designated NP&WS helipad - complete with fuel supply.
I was almost directly overhead when I spotted it, so I just circled left until it was the right distance away and then turned straight toward the centre. I wasn’t into wind, but I didn’t have much choice. Since I was sure I had the clearing made, I decided to leave the throttle closed.
Things had happened fairly quickly and I hadn’t upgraded to a “MayDay” or briefed the passengers. The helicopter didn’t have intercom anyway. The engine was still idling as we touched down, and the journalist leant over and asked me “Why are we landing here?” I let the machine slide to a stop and then said, “Because we’ve had an engine failure.” As soon as I said that, he opened the door and bolted - with the back seat passengers right behind him.
An overflying jet relayed my message to ATC that we were all okay and then I shut down. The ABC journalists were dubious about my explanation for landing because the helicopter looked alright to them and they knew the engine was still running when we landed. I offered to try for a replacement helicopter but they weren’t interested in going back up with me that day.
That night, back at Bankstown, Rex Sales Manager Ian Paull (now HAA Branch Chairman in Queensland) quizzed me about what had happened. Nothing made sense to me but I told him I was sure the engine had a major problem and wasn’t developing any real power.
The next day the machine was trucked back to Bankstown and the Allison 250-C20 engine was stripped. I saw photos later which indicated that the compressor was badly-eroded and a blade from the second axial stage had broken loose. The third axial stage compressor and stator vanes were badly damaged. The fourth, fifth and sixth axial stages were completely stripped and the centrifugal stage was damaged.
Essentially, the engine had been running on the first two axial stages and the damaged centrifugal stage. Surprisingly, there wasn’t much damage to the turbines. All of the stator vanes and compressor blades must have been shredded by the centrifugal stage and then melted or burned in the combustion chamber. How much power would have been available for the landing - if I had left the throttle open - is hard to say.
After having one complete and one partial in flight engine failure in my first 1500 hours of flying, I have now gone 21 years and 7000 hours without the slightest problem. I have flown multi-engine helicopters much of the last fifteen years and, as a result, I seldom get the chance to practice touchdown autorotations.
But I certainly think about the possibility of a donk quitting. In 1997, I ferried an AS350B from Sydney to Manila. The longest over water segment was 548 nautical miles. In late 1998, I ferried a Jetranger from the north island of New Zealand to Sydney via Norfolk and Lord Howe Islands. I certainly had a lot of time to think about the engine quitting when I was out in the middle of the Timor Sea or the Tasman Sea.
Air safety statistics prove that in flight engine failures are a pretty rare occurrence -- particularly with turbine power plants. My own experience tells me that power losses do not necessarily mean helicopter accidents.
On the other hand, safety statistics also tell us that engine failures are the most common mechanical factor leading to an accident. And I know that I owe as much to luck as I owe to Homer Youngblood and all of my instructors after him.
All of us in the Australian helicopter industry should be thinking about what we’ll do if the donk gives out whenever we are flying - irrespective of the number of installed power plants on the particular machine we are flying that day.
We should also be thinking about the issue when we are not flying, since we are currently confronted with CASA proposals for new legislation which could severely restrict the role of single-engine helicopters in commercial operations in Australia, and impose very stringent performance standards on multi-engine helicopter flying.
Like it or not, we are going to be forced to prove our bald assertion that helicopters are safe because they can autorotate following an engine failure. We are going to be compelled to consider the time we spend in the shaded portion of the height-velocity curve, and in areas outside gliding distance to a good forced landing area.
We are going to have to come up with compelling data to justify why we should be allowed to carry commercial passengers where there is a measurable chance of those passengers having to disembark from the top of a tree or swim for their lives.
Already, CASA has warned Sydney commercial operators that they should not be carrying commercial passengers in single-engine helicopters in Victor-One - unless floats are installed. The HAA hopes to be able to negotiate with CASA and Airservices over the designation of such routes and the rules that apply. But, for now, operators have been warned to comply with existing rules or face the consequences.
Personally, I believe that there should be a solid future for single-engine helicopters in commercial operations in Australia - notwithstanding European trends to the contrary. But unless we are all prepared to fly those single-engine helicopters as if the donk was about to give out -- unless we constantly minimise our exposure to the avoid portions of the height-velocity curve and continually look out for forced landing areas, formulating and revising our plan for an engine failure in our minds, as we fly along -- then we may find that the Australian accident statistics support the other side of the argument.
If that happens, we can look forward to more regulations, higher operating costs, and a shrinking market.
Is anybody in favour of that?
Daniel E Tyler
C/229th, 1970
"MID AIR"
All Rights Reserved