[Music] you know that feeling you get when you know that you have to perform at your absolute best that feeling of resolve determination but also maybe some nervousness about not screwing up well certain conditions can make Pilots feel exactly that same way and when you add on unreliable weather reports and an aircraft design feature working opposite to How it Should unpleasant things can start to happen stay [Music] tuned on the 5th of March of 2015 the northeastern part of the United States was in the grip of a major winter storm it had br BR with it significant amounts of snowfall over the New York area and was forecasted to continue to do so for a big part of the day but the poor weather did not stop the continuous stream of aircraft that were arriving and departing from the giant City's main airport and to keep that operation running the runway clearing teams at JFK and LaGuardia had been put on high alert already the day before and were now working hard with their plows and sweeping machines to keep the runways as safe as possible far south of New York in Daytona Beach Florida the weather was significantly more pleasant as a crew from Delta Airlines reported for Duty in the early hours of the morning they were about to start the second day of a 4-day trip together and on the previous day they had operated three flights before they reached dayona Beach for their night stop the pilots had then later enjoyed a dinner together at their hotel before going to bed at around 2100 to prepare for the early morning departure that they had scheduled on the following day both of them were feeling well rested and ready to fly again as they met up with their three cabin crew colleagues at around 0500 in the morning on the 5th of March to start their pre-flight preparation they were scheduled for another three flights on that day starting with a leg from Daytona Beach to Atlanta then onward to lardi airport in New York and then finally to Orlando where they would have their next night stop when they started reviewing their briefing documents they could see that the weather in New York was potentially going to be a problem but that is often the case during the winter months and normally not a major concern because when we Pilots are faced with poor weather at any of our destinations we will always first verify that it's good enough for planning purposes which is a set of visibility wind and Runway conditioned requirements that has to be within limits before departure if it is we will then make sure that our alternates are holding up as well and after that start planning on how much extra fuel it will take to anticipate potential Holdings for snow clearing or delays if the weather is not good enough well then we can still actually take off towards our destination but we will need to have at least two alternates with good enough weather instead we need that so if we reach our destination and the weather is still not good enough to land we can just divert to one of those alternates because we always operate this way we will never really take any chances we will always be able to land somewhere with enough fuel so when these two pilots were looking at the weather in New York for later on it wouldn't have bothered them too much the good news was that the weather in Atlanta and Orlando was looking fine and there were no other Nots or technical issues that was holding them back so they decided on the fuel for the first leg called that into the fueler and then proceeded to brief the cabin crew who was waiting to get out to the aircraft during the briefing the captain told the crew that the weather in New York was very snowy and warned them that this could lead to possible Holdings or diversions but that nothing else was out of the ordinary on the way out to the aircraft the the pilots decided that the captain was going to be Pilot Flying for the first leg so he started setting up the cockpit whil the first officer completed the walk around now these two pilots were both very experienced with the captain having flown 15,200 hours in total of which 11,000 of those had been flown on the aircraft they were now going to operate the McDonald Douglas MD-88 he was 56 years old and at the time of the flight he had over 9,700 hours of command experience before joining the airlines he had been flying the F-16 in the US Air Force where he had also served as a t38 instructor the first officer was 46 years old and had about 11,000 hours of Total flight time with 3,000 of those flown on the MD 88 he had previously flown on the boing 737 the boing 727 as a flight engineer and also as a pilot on the e2c Hawkeye for the US Navy the two pilots were getting along really well and the pre-flight went off without a hitch so at time0 557 a few minutes before schedule even the aircraft started pushing back for its first flight up toward Atlanta this flight was completely uneventful but the pilots knew that the real challenge of the day would likely be coming up on the second leg so they spent some time in the cruise looking through the forecasted weather again and doing some planning for that coming flight now before we go any further let's take some time here and talk about the aircraft that these two pilots were operating the MD-88 belongs to the second generation of the popular dc9 family it's a stretched version with two large JTA Delta 219 turbofan engines mounted on the AF part of the fuselage and because of that it's also equipped with a TAA tail the fact that the engines were placed in the back of the aircraft and much closer to each other for example on a boing 737 meant that the effect of asymmetric trust after a potential engine failure was much less severe due to a smaller moment arm this in term meant that the Roder could be made smaller and the fact that this smaller Rudder was situated so relatively close to the engines will have a very big impact on what's about to happen and why is that then well when an aircraft of this size is maneuvering on the ground at low speeds It generally uses nose wheel steering to do that this is accomplished by the use of a separate tiller in the cockpit but the nose wheel steering can also be accomplished to a smaller degree from the rudder pedals so normally moves the Ruder this is important because during the takeoff roll the pilots will be able to make small adjustments to the Direction with the nose wheel steering until there is enough air flowing over the rodder so that it can be used for directional control this happens when the Roder becomes aerodynamically effective above approximately 80 knots or 150 km/ hour now understanding this the fact that the rudder needs a lot of undisturbed air flowing past it in order to be properly effective is super important and I will tell you why after this a while back back I started noticing that I was getting more and more strange emails from companies I had never visited and even newsletters I had never 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yourself then click on the link here below which is incognito. com pilot right now they're running a special promotion which will give you an incredible 60% discount when you sign up for the annual plan thank you incog now back to the video so we have already talked about the fact that the engin are mounted on the back of the MD80 rather than under the wings and this comes with some advantages that the whole aircraft could be made lower making it easier for ground handlers to work on it and enabling a smaller and less heavy landing gear it also made it quite a bit quieter inside the cabin and gave it a much lower risk for foreign object damage fod since the engines were mounted further away from the ground but it also came with some negatives like the need to reinforce the back of the aircraft which came with some weight penalties and also made it more complicated for engineers to work on the engines on top of that the tail made the aircraft more susceptible to something known as super stall which is a very nasty aerodynamic situation that can happen if the aircraft stalls with a very high angular attack causing backwash from the wings to cancel out the effect of the elevators on the tail now none of those things will play a role in this story but something that will was another characteristics of its rear mounted engines you see larger aircraft uses several ways to slow themselves down after landing or in case of rejected takeoff they obviously have wheel brakes which works very similar to the brakes of your car equipped with anti- skid systems that senses wheel skids and reduces commanded brake pressure to always try and give Optimum braking then there are the spoilers on the wings which reduces or spoils the lift forcing the weight onto the brakes and also adds aerodynamic drag and then finally we have the trust reverses which are constructed to redirect the thrust Vector of the engines forward to achieve deceleration that way on the MD 88 the reverses consist of two bucket doors which are mounted on the back of the engine fairings on the ground when the pilot moves the trust levels back into the idle position that will unlock the two reversal handles which can then be moved backwards up to 120° when that happens the two bucket doors close behind the engines redirecting the entire air flow into slightly forward angles now these reverses are very effective and they work best at high speed but even at the stand still they're so powerful that they can actually be used to reverse the aircraft under its own power something that looks really really weird but those of you with a key eye might have already seen a small problem with this system if you redirect massive amounts of air forward from the engines at the position they are mounted that will pretty quickly start dis disturbing the air that is supposed to be flowing over the rudder and at higher trust reverse settings this becomes such a large disturbance that it can render the rudder almost completely ineffective an effect known as Rudder blanking this was quickly noticed during early flight testing and already back in the 1980s McDonald Douglas issued flight test report saying that this might happen and that it could cause issues with r directional Authority it was shown that below 108 knots these effects were no ible with a reverse trust setting as low as 1. 3 engine pressure ratio or epr and Below 146 knots if the reverses were increased to over 1.
6 CPR because of this the Delta flight crew training manual issued guidance to its Pilots to aim for 1. 3 epr reverse thrust on slippery or contaminated runways and never to exceed 1. 6 epr now the problem here of course is that it's precisely on slippery and contaminated runways that Pilots really need reverse thrust since the brakes will be significantly less effective then and monitoring the exact epr values during those kind of conditions can also be really challenging to deal with this McDonald Douglas had in 1996 sent out a service bulletin advising it to install a new type of revers or Cam that would include a detent which when it was used would reverse in an epr around 1.
3 to help the pilots out but only a year later they told everyone to remove this detent since several operators had found that the different engine riggings could make it difficult to accurately reproduce the expected DPR at the detent so now the pilots were again left up to their own devices to make sure that they looked after this and all Airlines operating the MD80 had approved training programs explaining this issue and allowing the pilots to practice it so it was well known by the crew this brings us back to the Delta crew which was now getting closer to Atlanta the first flight was completed without any problems and after the aircraft had landed and taxed into the gate the crew received an updated briefing pack as their passengers were dis embarking they could now see that the weather had not improved in fact it looked like it was getting a bit worse with moderate snow now forecasted all the way up until midday the latest weather report that the captain received indicated a wind of 330° at 12 knots visibility of half a mile in moderate snow and mist and with a cloud cover at 700 ft he was also given a notum issued at 0445 in the morning about the runway condition which stated that runways at LaGuardia were wet and that they had been sanded and treated with solid chemicals but what he didn't know was that another notom had been issued at 0738 saying that the runways were now snow covered with a thin layer of wet snow instead now these type of Nots which in Europe are known as snow ts are supposed to be issued regularly for airports where Winter conditions might have an impact P the idea is that they should be updated as soon as the runway condition changes and even if there's no change the time of the release should still be updated so the pilots and Airlines know that they're dealing with the latest information this was something that it later would be found out that laguard airport was not doing correctly Now by The Very nature these reports have to be taken with a grain of salt since they're only really valid at the time the report is written and might change within minutes if it's still snowing continuously therefore Pilots generally use them to calculate dispatch Landing performance and we all know that further updates will be needed before landing in any case as the crew were now getting ready for their departure towards LaGuardia they could see that the weather was still good enough to dispatch and that weather at their alternates were also holding up they calculated their dispatch Landing performance which included a 15% safety margin for a wet Runway and saw that they should be able to stop at 5,000 995 ft which was about 1,000 ft shorter than the available runway length of 7,3 Ft it was the first officers turned to be pilot flying on this leg but the captain decided that he would fly this flight as well due to the poor expected Landing conditions this shows that the crew was well aware of the threats here and that the captain had already mentally started to prepare for them he had actually been based at lagard a few years before and therefore had a lot of experience of flying in there even in Wind drops in any case they decided to carry a bit of extra fuel so that they would be able to hold for some time if they needed it the minimum fuel according to the flight plan was £ 26,000 but they decided to upload 3,600 extra just to be on the safe side now in previous videos that I've made about fuel emergencies I've been asked why Pilots don't just fill the aircraft up like we do with cars and there are actually several good reasons for that first of all aircraft are very weight sensitive and in most cases wouldn't even be able to take off if all the tanks were filled up to the brim with normal passenger loads I have actually only filled up the 737 completely once in my career and that's when I delivered a new empty aircraft from Seattle to Dublin but also it costs fuel to carry fuel around 2 and 1/2% per ton per hour so it's extremely uneconomical to be carrying around loads of extra fuel for no particular reason but but in this case there's also another factor that the pilots needed to keep in mind you see with extra fuel the aircraft would indeed be able to hold for longer but if that hold wouldn't materialize well then they would also be carrying more weights during the landing which would make their required Landing distance even longer so it's quite tricky to make these kind of decisions when you're dealing with winter obsess the conditions always tend to keep changing anyway as the pilots were having these discussions and preparing the aircraft for departure the cabin crew were boarding the 127 passengers who were booked on the flight among those passengers were two lap held infants who because they didn't have their own seats didn't have their own boarding cards either something that will become important later on when everything was completed the pilots called up air traffic control asked for clearance and started pushing back from the gate just a few minutes behind scheduled they tax it out normally and at time 09:24 Delta Airlines flight 1086 took off from Runway 28 in Atlanta and started tracking Northeast towards New York the aircraft climbed to its planned cruising altitude of 33,000 ft and once all of the paperwork had been completed the two pilots started turning their attention to the upcoming Landing about 1 hour and 10 minutes before the landing the cockit voice recorded pick up the first discussions regarding the complications that the weather would potentially bring them the first officer had started looking up the CR crosswind limitations and found that if the braking action on the runway was found to be medium to poor the maximum crosswind allowed would be 10 knots a value that they were already at with their latest weather reports now breaking action is the word that we use to describe how slippery the runway is and it's divided into six different levels poor medium to poor medium medium to good good and dry for each of these levels there are performance tables in our manual which gives us the landing distance required based on wind speed weight and a few other factors and when the pilots started looking into those tables they quickly found that with the weight they were planning to arrive with the runway would have to have a breaking action of good or better in order for them to be able to land if it turned out to be more slippery than that well then they wouldn't have enough margins to land and would have to divert to one of their alternates now an interesting fact here is that the way that the braking action is calculated it has changed over the last few decades it used to be measured using a special vehicle or wagon that was driven over the runway surface with a measuring wheel lowered down onto it which could break and then spit out a numeric value of how slippery it was this would then be transmitted to air traffic control and then to arriving and departing aircraft but the problem was that this tool had been found to be unreliable and not give data that would accurately describe how an aircraft brakes would actually perform form because of that this type of values had stopped being sent out to the pilots and was at this time only really used by the teams that were clearing the runway so instead of these wagons the FAA has suggested that some kind of device should be introduced that could accurately measure a landing aircraft's actual braking efficiency but even though several such devices were in development none had been officially approved so this meant that what the pilots were actually left with was in many Cas is just the description of the runway conditions ice wet snow or so on and from that they would then have to assess the braking action or rely on pilot reports from other Landing aircraft which could be very subjective now since it was obvious that the braking action on the runway was going to be critical for whether they would be able to land or not the crew sent out two different request for updates via their acar system one request went to their dispatcher in Lar where they also informed him that they wouldn't be able to land if the braking action was below good and the other one went to the artcc controller but neither of them had any updates to give them in the meantime the snow had started to accumulate on the runways in LaGuardia and at time 10:06 the runways were temporarily closed to allow for snow clearing equipment to come in and start clearing them up the clearing team quickly realized that it was no point in continuing to sand and treat the Run runways with chemical since they would have to periodically brush it and this would just remove any chemicals added this meant that the runway State Now quickly changed from the wet treated state that had been reported earlier to covered with wet snow less than 1 qu of an inch as the aircraft was proceeding along the Route the captain made a quick PA to the passengers and when he was done he needed to get to a quick bathroom break so he left the cockpit and was replaced by one of the cabin attendants who started chatting a bit with the first officer now whilst the captain was away the air traffic controller called the flight up and told them that they were clear to descend when ready to cross an arnab Point called ridy at flight level 270 the first officer read this back set it up on the mode control panel and then continued to chat with the flight attendant but only 2 minutes later the controller came back and told him to reduce the speed to a maximum of 250 knots over ridy since there was now a chance that they would need to take up a hold later on this was the first time that anyone had mentioned mentioned the possibility of a hold to the crew and the reason for the hold was explained as the runway now being closed at LaGuardia for snow clearing when the captain came back the first officer briefed him about The Descent clearance and the possibility that they might hold and this annoyed the captain quite a bit since the dispatcher had not mentioned anything about the runway being closed in his AAR message they started their descent as planned when they reach the top of descent point and it's likely that this news about the sudden Runway closure just further strengthened the captain's apprehension about Landing ahead of him and it was not getting any better the air traffic controller soon came back and cleared the aircraft to enter a holding over a VR called Robinsville and to await further instructions there they proceeded to watch the hold according to their Flight Plan and the controller soon came back and asked the crew if they could accept an eyess approach into Runway 13 the crew responded that this depended on the runway condition and the weather but the controller just repeated his question which confused the crew quite a bit they said that they could certainly fly the approach but the landing would depend on the braking action which they had not been able to get from any source so far the controller then said that he would come back with information when he received it and then cleared them to descend down to flight level 200 ahead of them in the hold they now had several aircraft who were already running low on fuel this prompted the crew to start reviewing their own fuel situation and decide on minimum fuel that they could St before diverting all handled like the professionals and experienced Pilots they were the first officer listened in on the 80s and received information Quebec which was recorded at 1051 this information reported a Runway to be covered with one4 of an inch of wet snow but that all surfaces were wet and treated with sand and deis with solid chemicals now according to the Delta winrs manual a wet Runway did per definition provide good braking action and and based on that the crew expected to see a black top runway with only patches of snow and ice on it but as we discussed before the clearing team had actually already stopped treating the runway with chemicals at this point but this had not been updated on the 80s the surface wind was reported at 03 0° at 11 knots meaning an almost straight crosswind and the visibility was marginal with the rvr just above the minimum for them to start the approach the aircraft eventually reach the Robinsville VR where they entered the hold and then continued to get descent clearances whilst they were in there the pilots were listening in on the radio traffic and soon one of the aircraft who had landed ahead of them reported that they had experienced poor braking action during the landing rooll this message was relayed bya LaGuardia Tower up to the area controller who transmitted it out onto the frequency and when the captain heard this he said we can't land with poor the controller then asked the aircraft ahead of them in the queue another under MD80 and a crj if they could accept poor breaking action for landing and they both responded negative but as this was going on an Airbus a319 was just about to touch down on Runway 13 so as the aircraft in the hold were now getting ready to divert the controller soon came back and said that another aircraft had just landed and reported braking action as good now these kind of things make decision making very difficult for Pilots because pilot reports are like I mentioned before subjective in nature and when you're about to land a 50 ton aircraft at around 300 km/ hour you really don't want the subjective assessment of how well your braking will work especially not on an airport like LaGuardia who has the ice cold water of flushing Bay located just beyond the runway end the controller asked the other aircraft if they were happy to continue and they all responded that they were as long as the braking action was still good the captain meanwhile discussed with his first officer who had reported good breaking action showing that he was well aware of the subjective nature of the report the first officer responded that it was the Delta flight and the captain was soon further calmed down when the second aircraft the crj also landed and reported the same thing soon after this the area controller told the crew to leave the hold and started providing vectors toward Final Approach at time 10:58 and 41 seconds they received a final turn a clearance to descend to 3,000 ft and from that altitude they were cleared for the ireless approach from 13 the crew configured the aircraft according to their procedures and as soon as they had established themselves on the approach they were instructed to contact LaGuardia Tower and also informed that the landing rvr was now between 4,000 and 6,000 ft the first officer read this back and as he changed the frequency over there was no update to the braking action the tower controller welcomed flight 1086 onto the frequency and then clear them to land but the captain who had now noticed that they had a quite significant Tailwind of around 11 knots asked the first officer to check for the latest wind the tower controller replied that the latest spot wind was 020 de at 10 knots which would mean a slight Tailwind component and when he heard this the captain just exclaimed oh jeez so why was this exclamation important well the pilots were both well aware of the fact that it was still snow knowing on the ground and with that the conditions could change rapidly they also knew that their Landing performance was calculated on good breaking action and that the calculation was already quite marginal with only a few hundred feet to spare any Tailwind would increase their ground speed leading to an even longer Landing distance and their crosswind limitation with a slippery runway was around 10 knots something that they were now on the edge of in other words it is very likely that the captain knew that he was facing several potential threats on this landing and that he therefore would need to perform on his absolute aame on the other hand none of these values were outside any specific limit so they were perfectly okay to continue the approach the pilots configured the aircraft for landing and then completed the landing checklist all of the flight parameters were stabilized as they passed through the landing gate at 1,000 ft and then contined down towards the Minima at 214 ft at time 11:01 51 seconds at an altitude of around 350 ft above ground the captain called out approach lights in sight and then 2 seconds later uh we're going to continue now that last call out was not required according to its Sops but what had happened here was that when the aircraft broke through the clouds the pilots saw something that they had not anticipated the runway ahead of them was not the black wet surface they had expected instead the runway was completely white and covered with snow no this would have further heightened the alertness of the captain and he likely made this call out to reassure his colleague who is now seeing the same thing remember all of the aircraft ahead of them had been Landing without any issues at this point the speed had now been reduced to their reference speed for flaps 40 plus 5 knots and at an altitude of around 188 ft the captain disconnected the autopilot and outo throttle to hand fly the last part the aircraft paused the runway threshold with a speed of 137 knots and at time 11:02 and 16 seconds the main gear touched down about 600 ft in on R 13 which would have been in the beginning of the touchdown Zone as soon as the weight on Wheel switches were activated and a wheel spinup was sensed the spoilers should have activated automatically but likely due to the slippery surface they didn't so the first officer activated them manually and called out spoiler toop about 1 second after main gear touchdown the nose gear was all Al landed and at almost the same time the first officer called out two in Reverse referring to the trust reverses which the captain had immediately activated upon Landing about 1 second later the first officer also called out 110 knots the runway heading was 134° and the aircraft touched down with a heading slightly to the left of 132° well within the normal range and now things started happening very quickly for the first few seconds the aircraft tracked the runway sent line reasonably well but then because of a combination of different factors the aircraft started veering to the left these factors included the effect of the left crosswind which was now pushing on the aircraft's fin making it starting to weather into the wind and on top of that when the captain selected reverse thrust the left thrust reverser activated slightly quicker than the right which also pulled the aircraft to the left the captain obviously noticed this and started to give right R to follow the center line but in his focus on making sure to get the aircraft toop stop he' made one big mistake instead of limiting the reverse thrust to 1. 3 epr he was Now using almost full reverse trust with the left engine ultimately giving 2. 06 CPR and the right 1.
