Centaurus
20th Jul 2013, 14:46
The circumstances surrounding the Asiana Boeing 777 that crashed at San Francisco airport on 7 July 2013, is well documented in Pprune Rumours and News forum. Sufficient to say the evidence so far, points to the crew failing to prevent the aircraft undershooting a visual approach with ever decreasing airspeed.
Why the crew allowed this to happen is still under investigation.
One avenue being looked at is the apparent lack of basic flying skills by the crew perhaps caused in some part by automation dependency. To let the airspeed fall back to 30 knots below the planned approach speed without taking effective correction action is mind-boggling to most of us – whether professional pilots or amateur.
Contrast pilot actions involved with the Asiana Boeing 777 accident with that of a former RAAF trained pilot who, when faced with an almost uncontrollable aircraft , had obviously retained his basic flying skills.
Flight Safety Australia magazine published the following contribution 14 years ago in 1999, awarding the writer $500 for the winning Airworthiness story.
It added: “The gratifying aspect of this tale is the skill and presence of mind that the writer displayed to land his aircraft given the significant control problems that were encountered. So, although the system let the pilot down, the basic skills which were developed during his initial pilot training and his subsequent experience, provided him with the depth of knowledge necessary to save this unusual situation”.
OUT Of CONTROL
In July 1951, when a DC3 first officer based in Melbourne, I went to Mackay, Queensland, with the object of ferrying a Tiger Moth back to Melbourne. The airline’s chief inspector was to be on the ferry for technical support. The machine was being purchased by a group of head-office employees as the nucleus of an independent flying club.
Rebuild of the aircraft had just been completed following damage sustained when a hangar collapsed during a cyclone. The owner carried out the first flight which I watched; everything was OK except that elevator control was still “offish”. By the time the elevator cables were fine-tuned the sun had set – there would be no flying until the next day.
As I had not flown a Tiger Moth for nine months a short flight would serve the dual purpose of providing familiarisation and giving a very helpful Mackay resident a joy ride. The runway was to be used because a series of deep ditches crossed the aerodrome for wet-season drainage. Checks were carried out in the usual DH82 fashion while taxiing. Flying controls were checked and found to be “free, full and correct as expected.
On take-off the machine waddled down the runway then leapt into the air of its own accord. I was suddenly aware of climbing with 30 knots on the clock, the auto slats standing open like the legendry clutching claws of fate and the aircraft’s nose still rising despite the fact that the stick was full forward. Not a pretty picture.
Three times around; To gain airspeed the machine was stood on its port wingtips: the nose dropped, speed increased and problem number one was solved. Problem number two soon emerged – the aircraft insisted upon a tight left hand turn which couldn’t be controlled with rudder; not really disturbing as a turn was necessary to return for landing. However, the left turn took us straight towards about six HF radio masts complete with aerials and guy wires.
Reduced bank produced a hop over that obstacle and a slipping descending turn was made to line up with the runway. Beaut! Except for problem number three, which became evident as the wings were levelled for landing, the nose popped up and we were climbing again.
The second circuit was like the first although speed was reduced to allow the wings to be levelled for landing; the reduction was insufficient and once again we were climbing.
Third time around proved lucky, the machine made quite a respectable landing by stalling completely as the wings came level. Almost a three-pointer; not bad after nine months.
Had anyone been interested, three circuits with the stick full forward in less than two minutes would have been some sort of record. I apologised to the local passenger for the scary ride, disgustedly kicked one tyre hard, and returned to Melbourne. Later the aircraft flew normally after correction.
So, what went wrong? The control box was incorrectly assembled and at some stage the down-elevator cables became slack. Elevator control on the Tiger moth is achieved by fore and aft rocking of a lever which is about 12 inches long (300mm) pivoted at its centre; up-and-down elevator cables are attached to the lever’s ends. Midway between the lever’s pivot and its lower end is a hole by which the control stick assembly is attached. All of this is below and slightly behind the rear seat. No inspection doors are provided, and the whole is concealed by the fabric over of the aft fuselage. Cables cross inside the fuselage and exit the side covers about halfway between the rear cockpit and the leading edge of the tailplane. The rod from the stick assembly was incorrectly attached to the lower extremity of the pivoted lever.
Elevator Control: The only attachment point available for subsequent placing of the up-elevator cable shackle was at the mid-point between lever pivot and lower extremity. Elevator control system geometry was altered and the down-elevator cable slackness could be introduced.
Back stick gave up-elevator correctly. As the stick was moved forward, slackness in the down-elevator cables allowed the elevators to fall under their own weight. On take-off as the stick was moved forward, the elevators took the streamlined position behind the tailplane and airspeed increased. Unknown to me was the fact that in straight and level flight the elevators are depressed by about 15 to 20 degrees.
With the elevators streamlined behind the tailplane, a strong nose-up pitch force is experienced by the aircraft. Hence the aircraft left the ground in a tail-down position. “Fine tuning” of cable tension was done by the Mackay LAME, my company chief inspector, and the most senior Queensland Department of Civil Aviation surveyor; obviously they believed the aircraft to be airworthy.
Fortunately I had received good training with the RAAF and RAF on Wirraways, Masters, Spitfires and Typhoons in authorised low flying, stalls, spins, aerobatics and recovery from unusual attitudes. All proved valuable.
……………………………………………………………………………………………….
Postscript.
The pilot of the Tiger Moth was former RAAF fighter pilot, Robert Birch. At the age of 20 Bob was flying Spifires and Typhoons with the RAF at the end of the war. He then joined TAA as a first officer and flew the DC3 and Convair 240. In 1957 he transferred to Swissair and flew the Convair 440,Caravelle, DC6 and DC7. In 1964 he joined the DCA Flying Unit flying the DC3, F27 and HS125 on radio navigation aid calibration duties. Then followed tours of duty with Iran Air and Japan Airlines where he flew the DC8
Contracts followed with Sterling Airways in Copenhagen flying the Caravelle. Returning to Australia, found himself living on Nauru flying for Air Nauru on the F28 and Boeing 727. His last job before retirement was with Alia, the Royal Jordanian Airline flying the B727. Then back home to Australia where Bob was engaged in ab-initio instruction and classroom lecturing before settling down in Yinnar South, Gippsland.
Captain Bob Birch passed away on 3 July 2013. He was 88. I knew him well.
Centaurus.
Why the crew allowed this to happen is still under investigation.
One avenue being looked at is the apparent lack of basic flying skills by the crew perhaps caused in some part by automation dependency. To let the airspeed fall back to 30 knots below the planned approach speed without taking effective correction action is mind-boggling to most of us – whether professional pilots or amateur.
Contrast pilot actions involved with the Asiana Boeing 777 accident with that of a former RAAF trained pilot who, when faced with an almost uncontrollable aircraft , had obviously retained his basic flying skills.
Flight Safety Australia magazine published the following contribution 14 years ago in 1999, awarding the writer $500 for the winning Airworthiness story.
It added: “The gratifying aspect of this tale is the skill and presence of mind that the writer displayed to land his aircraft given the significant control problems that were encountered. So, although the system let the pilot down, the basic skills which were developed during his initial pilot training and his subsequent experience, provided him with the depth of knowledge necessary to save this unusual situation”.
OUT Of CONTROL
In July 1951, when a DC3 first officer based in Melbourne, I went to Mackay, Queensland, with the object of ferrying a Tiger Moth back to Melbourne. The airline’s chief inspector was to be on the ferry for technical support. The machine was being purchased by a group of head-office employees as the nucleus of an independent flying club.
Rebuild of the aircraft had just been completed following damage sustained when a hangar collapsed during a cyclone. The owner carried out the first flight which I watched; everything was OK except that elevator control was still “offish”. By the time the elevator cables were fine-tuned the sun had set – there would be no flying until the next day.
As I had not flown a Tiger Moth for nine months a short flight would serve the dual purpose of providing familiarisation and giving a very helpful Mackay resident a joy ride. The runway was to be used because a series of deep ditches crossed the aerodrome for wet-season drainage. Checks were carried out in the usual DH82 fashion while taxiing. Flying controls were checked and found to be “free, full and correct as expected.
On take-off the machine waddled down the runway then leapt into the air of its own accord. I was suddenly aware of climbing with 30 knots on the clock, the auto slats standing open like the legendry clutching claws of fate and the aircraft’s nose still rising despite the fact that the stick was full forward. Not a pretty picture.
Three times around; To gain airspeed the machine was stood on its port wingtips: the nose dropped, speed increased and problem number one was solved. Problem number two soon emerged – the aircraft insisted upon a tight left hand turn which couldn’t be controlled with rudder; not really disturbing as a turn was necessary to return for landing. However, the left turn took us straight towards about six HF radio masts complete with aerials and guy wires.
Reduced bank produced a hop over that obstacle and a slipping descending turn was made to line up with the runway. Beaut! Except for problem number three, which became evident as the wings were levelled for landing, the nose popped up and we were climbing again.
The second circuit was like the first although speed was reduced to allow the wings to be levelled for landing; the reduction was insufficient and once again we were climbing.
Third time around proved lucky, the machine made quite a respectable landing by stalling completely as the wings came level. Almost a three-pointer; not bad after nine months.
Had anyone been interested, three circuits with the stick full forward in less than two minutes would have been some sort of record. I apologised to the local passenger for the scary ride, disgustedly kicked one tyre hard, and returned to Melbourne. Later the aircraft flew normally after correction.
So, what went wrong? The control box was incorrectly assembled and at some stage the down-elevator cables became slack. Elevator control on the Tiger moth is achieved by fore and aft rocking of a lever which is about 12 inches long (300mm) pivoted at its centre; up-and-down elevator cables are attached to the lever’s ends. Midway between the lever’s pivot and its lower end is a hole by which the control stick assembly is attached. All of this is below and slightly behind the rear seat. No inspection doors are provided, and the whole is concealed by the fabric over of the aft fuselage. Cables cross inside the fuselage and exit the side covers about halfway between the rear cockpit and the leading edge of the tailplane. The rod from the stick assembly was incorrectly attached to the lower extremity of the pivoted lever.
Elevator Control: The only attachment point available for subsequent placing of the up-elevator cable shackle was at the mid-point between lever pivot and lower extremity. Elevator control system geometry was altered and the down-elevator cable slackness could be introduced.
Back stick gave up-elevator correctly. As the stick was moved forward, slackness in the down-elevator cables allowed the elevators to fall under their own weight. On take-off as the stick was moved forward, the elevators took the streamlined position behind the tailplane and airspeed increased. Unknown to me was the fact that in straight and level flight the elevators are depressed by about 15 to 20 degrees.
With the elevators streamlined behind the tailplane, a strong nose-up pitch force is experienced by the aircraft. Hence the aircraft left the ground in a tail-down position. “Fine tuning” of cable tension was done by the Mackay LAME, my company chief inspector, and the most senior Queensland Department of Civil Aviation surveyor; obviously they believed the aircraft to be airworthy.
Fortunately I had received good training with the RAAF and RAF on Wirraways, Masters, Spitfires and Typhoons in authorised low flying, stalls, spins, aerobatics and recovery from unusual attitudes. All proved valuable.
……………………………………………………………………………………………….
Postscript.
The pilot of the Tiger Moth was former RAAF fighter pilot, Robert Birch. At the age of 20 Bob was flying Spifires and Typhoons with the RAF at the end of the war. He then joined TAA as a first officer and flew the DC3 and Convair 240. In 1957 he transferred to Swissair and flew the Convair 440,Caravelle, DC6 and DC7. In 1964 he joined the DCA Flying Unit flying the DC3, F27 and HS125 on radio navigation aid calibration duties. Then followed tours of duty with Iran Air and Japan Airlines where he flew the DC8
Contracts followed with Sterling Airways in Copenhagen flying the Caravelle. Returning to Australia, found himself living on Nauru flying for Air Nauru on the F28 and Boeing 727. His last job before retirement was with Alia, the Royal Jordanian Airline flying the B727. Then back home to Australia where Bob was engaged in ab-initio instruction and classroom lecturing before settling down in Yinnar South, Gippsland.
Captain Bob Birch passed away on 3 July 2013. He was 88. I knew him well.
Centaurus.