On 27 February 2001, both engines on Loganair Flight 670A flame out shortly after takeoff from Edinburgh Airport. The aircraft later ditches in the Firth of Forth, killing both of the pilots.
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00:00what did you do nothing did you hear those noises i did the audio playback of the copic voice
00:15recorder gave the investigators the first real clue as to the cause of the accident logan air
00:22670a loses two engines and crashes into the north sea both pilots are dead
00:30why would that trigger a dual engine failure it's never happened in the past serious aircraft
00:36accidents rarely have one causal factor it's a combination of circumstances here's something
00:43the crew called an engineer before departing well done why did the crew need to investigate a problem
00:50brace brace brace
01:00it's mid-afternoon on a chilly winter day at edinburgh airport in scotland
01:22several aircraft are preparing for departure including logan air flight 670a
01:32at the time logan air a scottish carrier was a franchisee of british airways
01:38it operates about 40 different aircraft and it does that in a variety of modes whether it's passenger
01:45or cargo to support a dispersed population anti-collision beacon anti-collision beacon
01:52on running through pre-departure checks is 58 year old captain carl mason
02:00and 29 year old first officer russell dixon
02:03the captain is hugely experienced he had royal air force training before he became a civilian pilot
02:19one two three first officer dixon passed his training with no failures or scrapes
02:28ignition fuel lever forward
02:32we have ignition 500 600 700
02:40the pilots are at the controls of a shorts 360 known as the shed and the flying shoe box for its unusual boxy
02:48shape
02:50the shorts 360 is a short haul commuter airplane
02:53which carries a total of 36 passengers and crew or approximately 8 300 kilos of freight it's a lovely airplane to fly
03:07moments after starting the right engine its generator stops let's try that again
03:16you carry out a set procedure to try and get the generator back online
03:20nine times out of ten that will solve the problem
03:30starting sequence finished stabilizing at 73 percent
03:38ah not again call maintenance the shed does this from time to time
03:44the shorts 360 is powered by two pratt and whitney pt65 engines
03:50they're a very reliable robust engine however you could have a fault with the generator where
03:56it will not be connected to the aircraft ac electrical systems all done
04:02perfect thank you the engineer gives logan air 670a the green light
04:08logan air 670a cleared for tala 5 delta standard instrument departure
04:19logan 670a tala 5 delta roger
04:25as the pilots taxi towards the runway
04:28auto feather test they complete final pre-departure checks
04:36feathering off
04:39today the plane is carrying more than 2 000 pounds of letters and boxes
04:45destined for belfast in northern ireland on a scheduled one hour flight for britain's royal mail
04:51prop levers maximum fuel levers flight
05:01logan air 670a prepares for takeoff
05:0680 knots roger
05:11v1 rotate
05:14at 5 28 pm the crew lifts off from edinburgh airport cycle landing gear
05:25it is prudent to cycle the undercarriage after takeoff in these conditions
05:30the slush can collect in the covers that the undercarriage retracts into
05:34as you climb this can refreeze as the temperature drops
05:41logan air 670a climbs as it approaches the north sea
05:48altitude
05:501 150 feet
05:53lots of white caps out there
05:56it's quite something isn't it
05:59the crew would have seen that the sea was rough
06:02they knew that the wind was blowing very very strongly because the aircraft was being buffeted about
06:10altitude
06:122 200 feet
06:15not two minutes after takeoff the crew takes preventative measures let's put the anti-icing on
06:21so precipitation doesn't form into ice in the engines and on the wings anti-ice both on
06:26what did you do
06:31what did you do nothing the captain realizes they're losing power in both of the engines
06:44we have a double engine failure torque is here on both engines
06:50dual engine failure
06:51the crew has little time to troubleshoot
07:08if you lose two engines you are not going to be able to maintain altitude so it is a very serious
07:13situation
07:14the captain initiates a right turn towards the coast looking for a safe place to land
07:21mayday mayday mayday mayday this is logan 670 alpha
07:25we've had a double engine failure repeat double engine failure roger logan air 670 alpha roger your
07:30airspeed 115 knots
07:40we can't relate the engines
07:42an engine in flight relight checklist would take three to four minutes for an experienced
07:47crew at minimum these pilots did not have time to do this
07:511300 feet 110 knots
07:54without power they're rapidly losing altitude
08:01altitude
08:03200 with the airport still three miles away and no suitable place to land on the coast
08:11captain mason has only one risky option prepare to ditch
08:16if i was going to be on a flight where everything was going to go wrong something like a dual engine failure
08:24captain mason is the guy i'd like to have in charge
08:27he has enormous experience in flying over the very hostile freezing cold north sea
08:36best speed is 110 knots i'll get us as close to shore as possible
08:39all they could do was to make the ditching as smooth and as slow as they possibly could without losing
08:52control of the airplane they had that task to perform if they performed it well they hoped they
08:58would survive their speed is 100 knots captain mason prepares the aircraft as best he can the captain
09:06increases the pitch to reduce the speed this will hopefully prevent the nose entering the water first
09:14and hence the aircraft flipping over logan air 670 alpha we are ditching send recovery send recovery over
09:25the radio call doesn't get through logan air 670 alpha do you read me logan air 670 alpha over
09:36it crashes into icy waters only 65 meters from shore
10:04the pilot is able to escape from the submerged plane
10:13it isn't until daybreak that the tide retreats and investigators are able to get a close look at the
10:19wreckage the flight deck was badly crushed
10:26the bulk of the rearmost fuselage and the tail units had broken away
10:34the aircraft was in a nose down attitude with the engines really stuck into the sand
10:42what could have caused both engines to fail just minutes after takeoff resulting in the deaths of two
10:49experienced pilots
10:50the uk's air accidents investigation branch or aai b immediately begins its investigation into the crash
11:04of logan air 670a please send those to hq salvage teams are able to recover most of the wreckage
11:13the start with the engine
11:17the first message i got was that the aircraft has sent out a distress call stating that they'd had a
11:22double engine failure our interest was very much focused on the engines
11:28while the recovered flight data and cockpit voice recorders are prepared for download
11:33investigators look for damage to the engines to explain why the plane crashed
11:45not a single blade appears bent
11:48there was no power on impact
11:51neither engine was working when the plane hit the water
11:54if an aircraft struck the water with the engines running the result would be bending of the
12:02compressor blades in the direction opposite to that of the of the airflow
12:08we found no evidence of such bending
12:10dual engine failure is unusual
12:15maybe it's something mechanical a problem or defect we can't see here
12:19we'll get the engines to the manufacturer we removed the engines from the airframe and shipped them to the manufacturer in montreal
12:31with a view to finding out whether there was any evidence of mechanical failure within the engines
12:43takeoff speed is normal with the data from the flight recorder downloaded
12:48the team scrutinizes the engine parameters for leads the climb is fine
12:56two minutes in look at that it looks like both engines flamed out at about the same time
13:08we have a double engine failure talk is here on both engines a dual engine failure is often due to
13:15pilot confusion not a mechanical issue to results usually of an engine failing for some reason or other
13:22followed sometime later by a second engine
13:26shutting down as a result of actions taken but applied to the wrong engine
13:34in 1989 the pilots of british midland airways flight 92
13:39shut down the wrong engine after a fan blade broke 13 minutes after departing heathrow airport in london
13:47the plane stalled and 47 people were killed
13:55there's no way the pilots accidentally shut down a second engine that quickly
14:00in this instance the shutdown of the two engines occurred certainly within seconds of one another
14:08which really didn't fit in with the scenario
14:16could you start 80 seconds into the flight just before the engines flame out
14:20the team now turns to the cockpit voice recorder for insight into the engine failure altitude
14:312200 feet let's put the anti-icing on
14:37anti-ice both on
14:38what did you do
14:44what did you do nothing
14:48we have a double engine failure
14:52did you hear those noises i did
14:56wonder what they could be i'll play it again
15:05let's put the anti-icing on
15:08anti-ice both on
15:14what did you do
15:17as soon as the first officer turns the anti-icing switches on there's humming noises
15:21and four seconds later both engines flame out
15:28the audio playback of the cockpit voice recorder gave the investigators the first real clue as to the
15:34cause of the accident
15:39what did you do
15:40nothing it was definitely linked to the two switch selections followed very shortly afterwards
15:46by the engines running down we have a double engine failure they're talking zero on both engines
15:51why would activating the anti-icing system somehow shut down both engines
16:04doesn't make any sense
16:05a a a i b investigators examined the anti-icing system of the shorts 360
16:20to determine if it played a role in the dual engine failure of logan air flight 670a
16:26and maybe the actuators failed
16:37electrical actuators operate mechanical veins that redirect ice and snow out of the back preventing ice
16:44from blocking airflow from blocking airflow to the engine when the veins are in operation
16:48they reduce air intake by 50 percent
16:55was the anti-icing system working
16:58investigators test another actuator to see if it matches the humming sound heard on the cvr
17:05before both engines flamed out
17:15well that sounds familiar
17:20tests on the actuator produced a tone which was
17:25similar to that detectable on the cockpit voice recorder of the aircraft
17:32should we compare it to the cvr
17:34mm-hmm investigators listened to the humming sound on the cvr
17:39to confirm it's the anti-icing actuator operating
17:50it's the same
17:52the matching sounds indicate the anti-icing actuators on flight 670a were fully operational
17:59as there was no other similar equipment in the aircraft that operated at that frequency
18:09the sounds must have been the result of operation of the anti-ice system
18:15why would activating the anti-icing system trigger a dual engine failure it's never happened in the past
18:24besides aircraft use anti-icing systems all the time
18:26aircraft anti-icing systems remove ice from control surfaces from the wing
18:34or from the engineer intakes and that just allows for the normal operation of the aircraft
18:40in pretty poor conditions
18:44if they were using the anti-icing systems maybe the weather played a part in the failure of the two engines
18:50investigators review the weather chart for answers
18:53for every 27th the crew lifted off at 5 28 pm
19:00no precipitation clouds at 4 500 feet winds 16 knots ground temperature is two degrees
19:10doesn't sound like icing conditions at takeoff no and the plane wasn't airborne long enough to accumulate ice during the flight
19:17hang on what about this storm overnight
19:24and maybe that had something to do with the engine failure
19:28it was quite a storm lots of snow
19:37a cold wind
19:41the weather was appalling it was gusting about 35 45 miles an hour
19:46it was snowing most of the time
19:53where was the plane during the storm
19:56the plane landed in edinburgh just after midnight on february 27th
20:02the crash happens later that day
20:04well that's right around the time the storm began and it took off at 5 28 pm
20:1217 hours
20:14is it possible the aircraft was parked outside in the snow the entire time
20:21let's talk to the pilot who landed the plane in edinburgh
20:24was there anything specifically that the previous crew did saw noticed or understood
20:34which may help them to actually understand what was the causal elements of this accident
20:41how can i help
20:44what happened when you arrived in edinburgh
20:47the aaib turns to the captain of the inbound flight for answers
20:52the weather wasn't great when we landed
20:58it was snowing and we could see the weather was going to get worse
21:02we taxied in and parked the plane at stand 31 with the other aircraft
21:06did anything seem abnormal with the aircraft nothing unusual at all
21:12once you parked the plane what next we supervised the refueling
21:18the plane was scheduled for de-icing
21:22but as you can imagine there was a backlog
21:29the plane was scheduled to be de-iced before the next departure
21:36attention all cruising passengers but then the airport was closed
21:40closing from midnight the snow started to become worse it was interrupting the snow clearing and de-icing
21:48operations and by two o'clock the airport authority elected to shut the airport down which was the correct and sage decision at that time
22:01how long did you stick around the airport after it was closed
22:05a few hours
22:07then at 6am we learned the airport wouldn't be reopening for a while so we secured the plane and clocked out
22:12it was shortly before dawn by then it was really blowing hard it was icy and there was snow everywhere
22:23the captain explains how the propellers were secured
22:27there are sock type straps attached to two of the propellers they are then attached to the side of the
22:33the fuselage which stops the propellers rotating in the wind
22:39after securing the plane we went off duty and that was it
22:46what about the engine intakes did you cover them with bungs
22:49the aircraft bungs are a blank which covers off the engine intake it protects the engine from the ingress
22:58of dust dirt particles insects snow and as such it protects the engine while the aircraft is parked
23:06well normally we would but there were no bungs
23:09bungs were available at the main bases of logan air but not at edinburgh so the flight crew had no
23:23means of protecting the air intakes
23:29right i think that's everything let me know if you have any other questions thanks will do
23:36the aircraft should be fitted with bungs if the machine was going to be left unattended for a lengthy
23:44period but edinburgh was regarded as a mere transit stop therefore no bungs were kept there and the
23:53aircraft didn't carry any bungs we know the plane parks here at stand 31 shortly after midnight when it
24:03was already snowing the airport closes two hours later due to bad weather investigators construct
24:10a timeline of the aircraft during the snowstorm according to the captain at 6am the crew secures
24:18the plane because the storm is still raging
24:24secured partially without bungs leaving the engines exposed and then the crew leaves
24:29the plane takes off eleven and a half hours after the first crew secured it
24:38what time did the storm end
24:43the snow stopped at 9 52 a.m the cold 30 knot gusts continued for a few hours
24:50and the temperature hovered just slightly above freezing by early afternoon
24:57that's 10 hours of exposure to snow ice and wind
25:06would that be enough time for a significant amount of snow to enter the engine
25:10what did you do nothing and somehow caused both engines to fail
25:25could exposure to a snowstorm for 10 hours have contributed to the dual engine flameout on flight 670a
25:32temperature wind investigators consider the impact of the wind conditions hovering around zero with winds
25:43from the northeast gusting up to 43 knots 43 knots that's a strong wind
25:50which way was the plane parked the plane was parked
26:03straight into the wind
26:06the team discovers the wind was blowing snow and ice directly into the plane's engines for 10 hours
26:12the aircraft had been parked in extremely nasty weather conditions with driving snow and ice pellets
26:22and the wind was consistently down the center line of the aircraft
26:27which exposed the intakes to have snow and ice pellets being blown into them
26:3510 hours that's a lot of snow
26:37true but once the engines are turned on it should melt
26:45so what's different here maybe it had something to do with the amount of snow accumulated
26:51could enough snow have accumulated in the engines to clog the air intakes and cause the crash of flight 670a
26:59mayday mayday mayday mayday mayday this is logan 670 alpha we've had a double engine failure repeat double engine failure
27:10one of the things which makes this accident a particular challenge for the investigators
27:17is that they're dealing with ice and slush and snows within the engine intake that disappeared into the sea during the crash
27:25brace brace brace
27:36without knowing how much snow collected in the engines
27:40investigators keep the possibility of an unrelated engine malfunction on the table
27:46pratt and whitney's detailed examination of the engines came in
27:49did they find anything there are no faults or defects with the engines
27:56as a result of the examination we were satisfied there was no evidence of any
28:01form of mechanical failure within the engines
28:03what about a compressor surge well that's an idea could happen if the airflow is restricted enough
28:17when airflow to the combustion chambers that power the engine's turbines is severely interrupted or restricted
28:30it can cause a compressor surge and can completely shut down the engines
28:34how restricted would the airflow have to be for the engine's compressor to surge i'll check
28:45aircraft engines require pretty much undisturbed airflow to work efficiently and effectively
28:52could both engines have been starved of enough oxygen to result in a dual engine flame out
28:58here we go for a compressor to stall and flame out the airflow into the engine must fall below 22 percent
29:07so that means
29:10snow and ice would have to block 78 percent that's a significant percentage
29:18a 78 percent reduction in airflow would explain why the engines failed on flight 670a
29:26could that much snow have accumulated within the engine's intakes to block 78 percent of the airflow
29:33let's find out
29:37the preliminary assumption that was made was that snow had built up within the intake system
29:44we needed some sort of assurance that this was a possibility
29:57i'll handle the snow you work the fan
30:02a aib investigators test how snow might accumulate and restrict the engine's air intake
30:08so we produced this mock-up of the engine intake system
30:18ready
30:22and we utilized an extractor fan to create the airflow through the engine
30:38the engine's air intake
30:47i'll check to see where it all went
30:56you're not going to believe this
30:57with the plane facing straight into the storm snow not only entered the engine's air intakes
31:08but made a 90 degree turn into the upper chamber
31:15these imitation snowflakes all consistently rose up to the top chamber and we satisfied ourselves that the
31:23air stream
31:23the air stream carrying the snow would have been capable of depositing all in the upper chamber
31:31the chamber is full of tubes and pipes the snow would likely stick to all that cold metal
31:38there are ducts pipes cables wiring and all of these provide ample opportunity for snow to adhere to
31:46to gather and given that the aircraft was exposed to these conditions for over 10 hours
31:53that was how we believe that the snow actually gathered undetected within that area
32:01but how would snow up here restrict 78 percent of airflow down here
32:06good point something else had to happen for intakes to be blocked 78 percent
32:12serious aircraft accidents rarely have one single causal factor
32:27there's usually a primary causal factor but in the end it's a combination of circumstances
32:35what happened between the end of the storm and the plane's departure
32:45here's something did something else happen to the snow-filled engines after the storm
32:52the crew called an engineer before departing one question for investigators was why did the crew
32:58call for the assistance of maintenance engineers to investigate a problem
33:02i'll talk to maintenance
33:16you help the crew with a concern before takeoff investigators questioned the engineer about the
33:22maintenance call to logan air 670a the day of the accident they called i went over to have a look
33:29the aaib learns the captain was having trouble starting the right engine
33:38let's try that again the right engine generator would not come online
33:49starting sequence finished stabilizing at 73 percent
33:53what this essentially meant was that the aircraft had half of its electrical power only and so the
34:03crew quite correctly shut down the engine and then called for maintenance assistance to determine what
34:08the problem actually was so what did you do i transposed connections on the generator unit and it restarted
34:15all done terrific thank you try running the engines for 30 minutes
34:25the crew carried on running the engines after it was apparently fixed
34:29i left and that was the last i heard from them
34:34the fact that the aircraft had been sitting around in in clement conditions overnight
34:39prop levers maximum fuel levers flights they may be seeking the confidence that the generator was going to stay online
34:55at 3 12 pm
34:58the pilots report the engine issue to the engineer
35:01he came at around 4 pm and got the right generator online then at 4 30 pm
35:09the crew runs the engines for 30 minutes 30 minutes
35:16investigators consider the impact of starting engines filled with snow and ice
35:21the heat from starting those engines would most likely have melted all the ice and snow in the upper chamber
35:32and then gravity takes over and it all slides down landing here right in the path of the air intake
35:38which means all that water and slush would have frozen into ice
35:49after the engines were turned on snow and ice inside the upper chamber likely melted and slid down to the air
35:57intake
35:58when the engines then idled for 30 minutes cold air entered the intakes re-freezing the water and slush
36:06into ice
36:08but is it enough
36:11was there enough ice inside the air intake to obstruct the airflow by 78 percent
36:17what else happened before the engines failed the last thing they do before the engine failure is turn on the anti-icing system
36:32altitude
36:32and when the anti-icing is turned on to clear the air intakes
36:47when the anti-icing vein operates air flow is reduced
37:01it would explain why the engines failed
37:14the total blockage of the air flow
37:16blockage of the air flow is sufficient to cause the compressor to surge in the engine flaming out
37:25and the complete loss of power
37:27we had two very well qualified crew on the day
37:31and it was an alignment of circumstances that they could not see or foresee
37:36captain mason and first officer dixon arrived at edinburgh airport long after the snowstorm had ended
37:43anti-collision beacon
37:45anti-collision beacon on
37:46they had no idea that their engines were filled with snow
37:56the snow had melted from the fuselage
38:06start master armed engine start sequence
38:09they took all the right steps at takeoff
38:17they did nothing wrong
38:20but what about after the engines failed
38:26could the pilots have found a way to save their plane
38:30airspeed 115 knots
38:33we can't relate the engines prepare to ditch
38:39this is the final minute of the flight
38:52investigators return to the flight data
38:55to determine if the crew followed proper procedures after losing engine power
39:03once the engines failed the pilots needed to relight the engines to make it to land
39:07right run a dual engine failure checklist
39:14we have a double engine failure talks at zero on both engines
39:20dual engine failure
39:22but the only checklist available was for a single engine failure
39:30dropping fast from 1600 feet captain mason probably knew that he didn't have time to relight the engines
39:37airspeed
39:39airspeed 115 knots
39:42we can't relight the engines
39:451300 feet 110 knots
39:51they had no choice but to ditch
39:57altitude
39:58did the pilots do everything they could to ensure a successful ditching
40:07uh ditching ditching there's no ditching procedure for dual engine failure
40:13ditching with power then we're gonna have flats so aiming for lowest possible speed
40:21without any engine power the hydraulic systems would not be operating
40:25the hydraulics drive the flaps which means he had to touch down at a higher speed than he would like to do so
40:32as i get closer i'll increase the pitch to nine degrees
40:36anything i'm missing that's it
40:38without flats the only way you can reduce speed is to increase the angle pitch of the aircraft prior to touchdown
40:50his actions were correct
40:52the captain tried to reduce the impact with the few resources he had at hand
40:59you hope it kisses the surface of the sea rather than thumping into it
41:03airspeed is 110 knots
41:07okay this is as close to sure as possible
41:10the slower you can go the safer the ditching is likely to be
41:16the successful ditching also requires level wings on impact they nearly pulled that off
41:22airspeed airspeed is 88 when the aircraft touched the water surface one wing was three degrees lower
41:36than the other that's a very very small amount from the time he identified the problem to the moment
41:42the plane hit the water the captain nailed every single action correctly
41:52they were very professional and they showed excellent prioritization
41:58the captain especially his experience clearly showed brace brace brace
42:13i have immense admiration for this crew because they found problem after problem which they couldn't have foreseen
42:22they handled the situation absolutely as well as any crew could possibly have handled it
42:30this investigation reveals the checklists for double engine failure and ditching without power were missing from the logan air operation manual
42:48the results of this accident was the tragic loss of two crew who had been doing their best to follow procedures
42:55the airline also didn't adequately reflect the manufacturer's advice for protecting the engine's intakes during severe weather conditions
43:05if the airline had followed the recommendations of the manufacturer and carried on board air intake bungs
43:14for the crew to use when the weather conditions demanded then this accident would never have happened
43:22the aaaib recommends that flight crews are educated about the potential of ice and snow build up inside engines
43:30i think the most important recommendation was that crews must be alerted to the fact that there's a possibility
43:37that snow would have built up in parts which are not visible to them by simply looking through the air intakes of the aircraft
43:46this was a very regrettable accident their fate had been sealed by an alignment of circumstances
43:54that whilst difficult to recognize were avoidable