What if the reversers OPEN in flight?!

hi everybody better welcome to mentorians about the video podcast as always I hope you're doing absolutely fantastic today on the video guys we're going to be talking about trust reverses what are they used for how do we use them and what would happen if a trust reversal was deployed in flight stay tuned this video is brought to you in cooperation with brilliant dot-org now brilliant dot-org will help you to sharpen up on your math skills and understand the essentials of physics in a fun and educative way so the ones of you who are really quick and uses this link here below the 501st of you who get 20% off the annual fee are brilliant but as always it's completely free to check it out and I guarantee you that if you do you'll find it really interesting [Music] right guys so trust reverses this is a fascinating subject and it's stuff in here that I guarantee you that you didn't know about them I get a lot of questions regarding trust versus when I'm out flying and generally air passengers time to ask what is all that noise that happened just off the landing and why does it look like the engines are splitting in two just off the landing now in order to understand thrust reversers we have to start with why we have thrust reversers in the first case easy you say it's because we need to reduce the landing distance but that's only partially true all right essentially the thrust reversers will only reduce the landing distance on a slippery or a wet runway if it's on a dry runway the truss traverses doesn't reduce the landing distance at all so why do we see aircraft doing that then this is a question actually got on my facebook channel just a few days ago well why are some airlines using a lot of thrust reversers even on a hot and dry day and why some doesn't well here is where we get into some of the interesting bits to 'trust reverses now if you think about it an aircraft that's coming in to land a 737 for example might be lad might be about 60 to 63 tons on landing it's common in at landing speed of about 300 km/h about a hundred and fifty knots or so that is an enormous amount of energy that needs to be reduced down to zero before we can taxi off without the trustor versus the only thing that will take up all of that energy are the brakes now the brakes are only efficient when they are cooled the hotter the brakes becomes less efficient the braking will become this is why when you look at sports cars for example the the hyper cars they always have little air dots that lead air in to cool down the the brake discs it's the same on an aircraft but we don't want that and especially if you are working in an airline that does very quick turnarounds we need to be able to reduce that temperature on the brakes as much as possible so that the aircraft can be around breaks can be cool enough to take off again on the next flight so thrust reversers will be used in that case as well but not to reduce the landing distance but to reduce the brake temperature all right so this is what we're doing on a nice hot summer day when you hear a lot of reverse thrust being used is to reduce the the temperature of the brakes in order to enable a quick turnaround if we have a long turn around well done this enough time for the brakes to cool down by itself in that case thrust reversers will only be selected to idle but never less than idle and I'll explain that in a second so how do we use them done well if we start in the case of a take-off you might know by now that an aircraft needs to have a decision speed there needs to be calculated before before we go a v1 speed which is the highest speed at which we can still reject the take-off and get to a stop within the available runway distance or the lower speed to which we can start a takeoff would an engine failure and continue to fly alright so we do that calculation on the ground before we attack see out now if we decide to reject the takeoff that might be because of an engine failure or because when I knew fire or because the aircraft is unsafe or unable to fly or a predictive windshield warning well in that case we have to get the aircraft stopped right the thrust reversers are actually not part of the calculation on the rejected takeoff but like I mentioned before they're still there to help to reduce the brake energy so the way that a rejected takeoff is performed if you want to see exactly how that is done I recommend it to go into the mentor aviation up and you can see just get the rejector take off an emergency evacuation collection in there and you'll be able to see in 360 exactly what the captain does and what the first officer dove how we do it and how an evacuation is performed you'll be able to see it in 360 so you can use your phone or your your tablet and you can use a finger and swipe around or you can move the phone around to see the entire cockpit or if you have a Google cardboard VR headset it will be just like you're sitting on the jump seat together with me doing the manoeuvre anyway that's the rejected takeoff and the as you will notice there the verses are only selected at the last point so that's because they're not included in the calculation now on the landing it's different on the landing we always select reverse trust always okay the way that the landing is performed would would reverse trust in mind is that when you get into the flair ideally the trust of a the thrust levers should be closed back to idle when we touch down so in a perfect landing the trust is completely closed just as the main gear touches down now on main gear touchdown provided that we have the trust reverse is closed we will select the reverses to to idle now the reverses are those little levers on the front on the front of the main thrust levers so close the trust levels select the trust reverses it will take a few seconds for the thrust reversers to activate and on the 737 what you will see is how a panel on the engine is sliding back and showing some cascade vanes when the mechanism is fully ready then you will see two indications above the n1 indication on the engine display turn from amber to green when that's happening then we select whatever trust reverse we need so if we don't need reverse trust we will leave it in idle to have it there if we need it but in most cases if we're doing a quick turnaround for example we select second the turn Traverse trust so that's from idle up to the first click and that will give us about seventy three percent and one reverse trust now if we need full reverse thrust so let's say that the runway is slippery for example well then there's another detail to click once more and that will give us a t2 and that's the 82% and one is the maximum reverse trust available on the 737 and on landing then it does make a difference okay so on a dry runway no difference on a wet runway or a slippery runway the trust reverses might actually be the only thing that gets the aircraft to stop because the the brakes have an anti-skid system basically the way that brakes works is that if it feels that the wheels are skidding which will do very quickly on a slippery runway well then brake pressure is removed from the brakes so if you're landing on a braking action which is medium to poor for example as soon as we apply brakes the anti-skid is going to release it okay and we won't get any braking from the wheels and in that case the trust services are essential and we need to have them full reverse thrust because that is essentially the only thing that gets the aircraft to stop very very important okay and this goes on taxiways as well we are able to use the trust services whenever we need it in order to get the aircraft safely stopped so so when do we cancel it then well on landing because of this what would do is on a dry run way or with braking action good we reduce the trust from whatever trust reverse that we've used down to idle add around sixty sixty knots but we don't cancel it okay it still sits at idle until the captain is absolutely sure that we're back to taxi speed and we can fully stop the aircraft is needed to only dam or thrust reversers cancelled so put flush down again the reason for this is that you might find that for example if we're landing on slippery runway they might have cleared the runway very nicely in the middle of the first of the second third of the runway but at the last one that's when the the machines that are clearing the runway tend to slow down and maybe make their turns to return so it might become really really slippery to watch the end of the runway and of course if we have done camps in the trust and we need it again well then the whole thrust reverser mechanism needs to be unlocked open and that might take up to 15 seconds to achieve full reverse thrust again and that is more than what we have so that's why we sit with idle so if we turns out that up what it's more slipper than I thought we immediately select reverse trust again okay now they're different reverser types so I will just briefly mention turboprop aircraft those are the it tends to be smaller aircraft that has propellers instead of fans now those propellers have variable pitch on the propeller so it's kind of like the the gears in your bicycle you know if you vary the picture that if the the propellers taking bigger slices of air it'll be heavier for the engine but it will also produce more thrust okay if you take smaller slices of air you'll be able to go you know climb for example more efficiently but it will not produce the same amount there's a there's a lot of theory behind this but essentially because you can't vary the pitch of the propellers it means that you can put them into beta which is instead of producing backward trusts you can now produce four trusts which is an extremely efficient way to create reverse thrust right this is fundamentally different from how jet engines produce reverse thrust so on you'll see on for example the MD McDonnell Douglas 80 or 82 and some of the Gulfstream aircraft as well you have what we call bucket type reverses these are reverses that extend from the back essentially they're hydraulically operated buckets that move hinged back and they block the entire thrust from the engine and redirect the trust for but at an angle of about 135 degrees these are very very efficient traverses and they tend to be used on engines with slightly less bypass ratios like these smaller engines for example on engines like on the 737 and the Airbus 320 and bigger aircraft type as well well then we use the bypass air to reverse the engines so in that case instead of blocking the entire backwards motion of the air then we essentially put down doors in the bypass duct and as I mentioned before my videos the bypass air actually represent about seventy percent or up to seventy percent of the trust of the engine so if we block the bypass air and we open cascade veins we'll be able to redirect all of that air that comes from the fan forward not also about 135 degrees and that is also a very efficient way of achieving reverse trusts so those are essentially the three different types of reverse trust that you will see and this is why you will see the the engine kind of opening up after landing and also this is why you hear the engine rev up because once the mechanism is in place we'll then we need more trust to direct it forward in order to be efficient but what about trust reverse in flight then can you actually select your vs. in flight the answer to our question is yes and no so there are aircraft types that have the capability to select reverse trust in flight they tend to be mmm turboprop aircraft quite a few of the military transport turboprop aircraft like the likely Hercules for example and even jet turboprop aircraft can select reverses to a certain extent in flight and that is made in order to be able to do tactical high rate of descent this ends in e for example enemy territory where you will need to get down quickly and land it is not very comfortable it creates a lot of buffeting a lot of vibrations in the aircraft but it is very efficient there were also some older type aircraft like the dc-8 that was able to traverse in flight to achieve the scent rate of ten thousand feet per minute if needed - and even the the Concorde is rumored to have the capability to reverse two of its engines in flight in order to also achieve around ten thousand feet per minute descent rates but modern transport aircraft like the the Boeing 737 and the Airbus 320 for example they are not able to do so in fact it is completely prohibited to use reverse thrust in flight it is mechanically locked and hydraulically locked in flight and those locks tends to be connected to either the weight on wheels switches and the switches that are connected to the landing gear that feels the landing gear being compressed and only then are you able to select reverse thrust or in the Boeing 737 it actually is also activated by the fact that the trust levels are closed and you're below 10 feet Radio altimeter then the thrust reversers are able to be unlocked but we're not allowed to do it in flight but hey some of you would say I've seen a bit YouTube video of a 737 who selected the reverses in flight and yes so since the 77 can select the truss reverses at 10 feet it can be done and the video that went viral of you I think about a year back of an aircraft coming in in a very you know it was basically in a severe storm in the UK did select reverses just prior to touchdown it's not approved to do that but you have to put yourself in the indy kind of mind of the pilots the pilots are coming in it's severe crosswind high gusty winds and they're very very concentrated on getting the aircraft exactly touchdown quickly get reverses off to get the aircraft down to speed but it is fully controllable ok so it is very possible that in that circumstance the pilot jumped the gun a little bit selected it a little bit prior to touchdown and if you do that it will produce a fairly firm touchdown all right so it's not something that is recommended or allowed to do but if you for whatever reason would have a mechanical failure or you wouldn't require several mechanical failures in order to put the trust versus to inadvertently be selected in flight well then you have a problem the the way that the aircraft was tested out was that they are supposed to be controllable at low altitude with one thrust reverse is selected at idle trust it will create a lot of jaw it will create a lot of a symmetric trust obviously and an extreme amount of buffeting but you are supposed to be able to control it at low level because that's when you have more authority of the rudder in the back we have a non normal checklist a cure a checklist that we can use in that case and essentially it will guide us into shutting the engine down that has the truss reverse activated if that would happen at high altitude at like our cruising level where we are very close to both high speed and low speed buffeting you would have seen that in my episode about what happens if an aircraft climbs too high then it is highly likely that the pilots would lose control of the aircraft very quickly and there has been instances where this has led to real accidents there was a very famous incident that happened back in 1991 where a louder air Boeing 767 got the truss reverser deployed in flight and the pilots lost control of the aircraft and it basically spiraled out of control broke up and killed everyone on board and there's been other accidents as well so after each of these incidents and accidents the safeguards have been made better and better by the aircraft manufacturers and now there should be very very small risk of this ever happening in real life right guys that's what I had about trust reverses I'm guessing that you have more questions about this as always send them in below or if you want a straight answer for me directly well then go into the mentor aviation app chat and just tag at mentor that would send a that question or that message directly to me and if I'm available if I'm not out flying I'll be able to answer it or you can ask any of the other commercial pilots that are inside at the Apple is there to help you answer all of your questions I want to send a special thank you to the long-term sponsors of the channel which is brilliant org now of course that I think that you guys will enjoy is science essentials where you will learn everything about different measurement units and how to properly apply the scientific process in order to solve a problem something that brilliant have just started with as well that I think that you really enjoy are these daily problems that they will send out essentially instead of sitting on the subway just kind of idly checking Facebook you could be rubbing your brain cells and him trying to solve a problem and if you can't solve that problem as always 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Channel: Mentour Pilot

Views: 1,219,636

Keywords: How to become a pilot, pilot life, mentour Pilot, Reversers, buckets, aviation, avgeek, aviation facts, Aviation knowledge, ATPL, Cadet, First officer, Captain, Boeing, Boeing 737, Boeing 737MAX, Airbus, Airbus 320, Airbus 380, Concorde, DC 8, Hercules, Military aircraft, Landing, takeoff, Aircraft brakes, flying, flight, Fear of flying, Aviation Youtuber

Id: OguKthkuaT4

Length: 20min 25sec (1225 seconds)

Published: Fri Jan 11 2019