The DEADLY Secret That Ripped This Plane APART! | Dan-Air Boeing 707

Early in the morning on the 14th of May 1977, a flight crew from the British airline Dan-Air reported for duty at Nairobi Airport, Kenya, in order to pick up a shipment of cargo that was arriving from Athens. They were then supposed to fly their red and white Boeing 707 onwards to its final destination in Lusaka, which is the capital of Zambia, where they were then supposed to deliver that cargo. Now, this type of non-scheduled cargo operation was common for Dan-Air, which was a jack-of-all-trades airline that operated everything from regular passenger flights, tour charters, to oil extraction support flights, and everything in between. And that meant that Dan-Air crews sometimes got sent to some pretty far away places. So, having rested for 30 hours and then made all of the necessary preparations for this flight over to Zambia, the crew soon walked out and met the arriving airplane on the ramp as the previous crew was disembarking. The crew that was now about to take over consisted of a 34-year-old captain who had recently transferred over to the 707, then a very experienced 57-year-old first officer, a 38-year-old flight engineer instructor, and a trainee flight engineer, along with a load master and a ground engineer. Now, I usually go into the backgrounds and experience of the flight crews in these stories, but this time I won't because the main character in this tale is actually the aircraft itself and not the crew. This was a 14-year-old Boeing 707-321 Charlie, built back in 1963 as a convertible passenger freighter aircraft, and then registered in the United Kingdom as Golf Bravo Echo Bravo Papa. The four-engine 707 was the first American-built jet airliner which had revolutionized air travel when it first entered service back in 1958. And over a 20-year production run, numerous improved variants had then been including the 320 Charlie series. Now Golf Bravo Echo Bravo Papa was the first ever 707 320 Charlie series aircraft to roll off the assembly line and it was one of several originally delivered to Pan Am where it had served as a passenger aircraft until March of 1976 when it was withdrawn from service and placed into storage in Florida. Later that same year Dan-Air had acquired the airframe, flown it over to the UK and then overhauled it after which it had began operating for them in October of 1976. Now the 320 Charlie series was fitted with both passenger amenities and a cargo door in order to allow easy conversion between passenger and freighter configurations and that had made it into the most popular 707 variant since passenger airlines believed that the cargo door would increase the plane's resale value. But at the time of this story this aircraft was operating as a pure freighter for Dan-Air's cargo division. Anyway, back in Nairobi the flight crew soon finished up the walk-around inspection as well as the various pre-flight checks and had found no anomalies. So they soon proceeded with refueling and then continued preparing the aircraft for the flight. All the onboard cargo had originated in London and no new cargo would be added in Nairobi so the turnaround was fairly quick. This in turn meant that at 10:17 local time the aircraft lifted off again into a perfectly blue sky soon turning south for the approximately 2-hour long flight over to Lusaka. As it then climbed to its cruising altitude of 31,000 ft and leveled off everything on board seemed perfectly normal. The plane was handling fine, all major systems were working with zero problems and weather was great with only a few scattered fluffy cumulus clouds dotted along the route. But this seemingly normal picture hid a very troubling truth. This airplane was actually kind of a ticking bomb at this point, which was now counting down its final minutes. But the origin behind that had not started on this flight over to Lusaka. Instead, it had actually begun more than 20 years earlier, in the late 1950s, when Boeing was designing the first Boeing 707. Back in those days, the science of aircraft structural design was really in its infancy. Only a few years had passed since the infamous downfall of the de Havilland Comet, the world's first jet airliner, which had suffered two catastrophic crashes in 1952 and 1954, after de Havilland had dramatically overestimated the safe life of the aircraft's pressurized fuselage. You see, the greatest threat to an aircraft structure is often metal fatigue, which is the tendency of metal to lose its strength and start cracking when subjected to large numbers of

repeated load cycles, until eventually it fails entirely. When the Comet was designed, engineers had estimated the number of pressurization cycles that the fuselage could withstand, and their calculations showed that each airframe would retire well before that number was reached. This was following a structural design concept called safe life, which was the only method for assuring the safety of an aircraft structure at the time. But as we now know, determining the safe life of a structure turned out to be way more complicated than the de Havilland engineers had thought. And the consequences when they got it wrong were disastrous. As a result of that, regulators and manufacturers soon introduced a second safety assurance method called the fail-safe concept. The idea here was that the uncertainties of the safe-life concept could be mitigated if structural elements were fail-safe, meaning that the failure of any one single primary structural element would be mitigated by a second element, and therefore not cause a catastrophic fault. In practice, this meant designing redundant secondary structures that could absorb flight loads after major failures, combined with inspections intended to detect any obvious failure of the primary structure. Due to the experience with the Comet crashes, essentially all airliners designed during the late 1950s, '60s, and even into the 1970s used the fail-safe concept for all major structures. And one of those aircraft was the Boeing 707. Now, the part that we want to focus on here is the 707's trimmable horizontal stabilizer, which is what gave the airplane its longitudinal balance. Basically, this is what prevents the aircraft from randomly rotating nose up or nose down about its center of lift. You see, essentially, the whole airplane is like a seesaw, balancing based on its center of gravity, which is where the airplane's whole mass can be thought to be concentrated, and its center of lift, which is the point where the lift from the wings is acting on the airframe. Now, one way to balance the plane is to make sure that the center of gravity is exactly lined up with the center of lift, which is what Concorde did. But, that's really hard. So, instead, normally, the center of gravity is deliberately positioned forward of the center of lift, introducing a nose-down tendency, which is then counteracted using downforce from the horizontal stabilizer on the tail, and that provides a stable margin, which will allow for the weight inside of it to shift a little bit of a time without the aircraft becoming unstable. Now, the stabilizer acts like an inverted wing that generates lift pointing downwards instead of upwards, leveraging the entire airplane like jumping on the seesaw opposite to your friend. The amount of downforce generated by the stabilizer can be changed by tilting it up or down or trimming so that the plane can be balanced anywhere within a range of possible center of gravity positions. For this story though, what's important to understand is that in order to generate this constant downforce, the stabilizer has to be subject to a continuous downward aerodynamic load from takeoff to landing. And it must therefore be strong enough to withstand that load across tens of thousands of flights. And that brings us to the design of the first horizontal stabilizer used on the original Boeing 707-100 and 200 series. But before I get to that, most of the accidents that I cover on this channel have something in common. The crew didn't know that they were in any danger until it was too late. Sure, there might have been some warning signs, but a lot of times those were either ignored, dismissed, or misunderstood for some reason. Now, that exact same thing happens online every day to unsuspecting people all over the world. You maybe click on a link, land on what looks like a perfectly legitimate website, enter your details, and boom. By the time you realize that something is wrong, the damage is already done. And that is exactly why I use today's sponsor, NordVPN. Their threat protection pro feature does all of the heavy lifting for me to make sure that I stay safe online. It scans every website before it loads, blocking fishing sites, fake shops, and malware before they can do any harm. And you won't even need your actual VPN activated for it to work. It just runs constantly in the background. Nord is the only VPN to be recognized by independent cybersecurity testers, so you know that you are in good hands. And if you want that extra layer of protection as well, well then scan this QR code or head over to nordvpn. com/pilot for four extra months off your two-year plan. And remember, with Nord's 30-day

money-back guarantee, you can try it out completely risk-free. Thank you, Nord. Now, let's get back to that first horizontal stabilizer on the Boeing 707. Now, the horizontal stabilizer is basically just a metal box made of aluminum skin stretched over the top and bottom of a framework consisting of lengthwise spars and crosswise ribs for rigidity. The original 707 stabilizer was then attached to the vertical tail by four attachment points, two on the front spar and two on the rear. Now, those front and rear spars form the front and rear edges of the box structure, and all of the downward bending loads on the stabilizer were transferred into the aircraft by passing through the spars and then through those four attachment points. Should a spar fail, it would lead to the destruction of the horizontal stabilizer, a loss of pitch stability, and the loss of the aircraft. So, Boeing had therefore designed the spars according to the fail-safe concept. Each spar was built with both a top chord and a bottom chord, which were basically separate beams connected by a thin metal web material. In normal flight, 95% of the downward bending load was transferred through the rear spar, with the top chord in tension and the bottom chord in compression. The rear spar top chord attachment point was therefore under the most stress and was seen as both a point that was most likely to fail and the most critical failure point in terms of possible consequences. Therefore, Boeing proved through real-world load testing that with a rear spar top chord attachment point disconnected, the downward bending loads on the stabilizer would be redistributed through the intact forward spar. Whilst the rear spar bottom chord attachment point would not fail, and the stabilizer would remain attached to the aircraft, meaning redundancy. And since a failure of an attachment point was expected to be obvious, such a failure would therefore then be detected under Boeing's prescribed inspection program and fixed before it could cause any accident. Now, as far as we know, this concept worked well for the 707-100 and 200 since no serious structural problems with the stabilizer were ever reported on those aircraft types. But the same could not be said for the 707-300 and 400 series, which included this aircraft. So, let's have a look at why. When Boeing was designing this next generation of 707 aircraft in 1959 and 1960, they made a number of changes to the horizontal stabilizer. In order to accommodate the 300's longer fuselage, the stabilizer needed to produce more downforce. So, its area was therefore enlarged, but that also meant that the aerodynamic loads on the structure would become higher. And in order to compensate for that, whilst maintaining the fail-safe nature of the structure, Boeing added a middle chord to the rear spar in between the top and the bottom chord, complete with its own attachment point. Now, this middle chord and its attachment point were designed not to carry any loads when the structure was intact, but the idea was that if the top chord would detach, well then the middle chord would take up some of the tension instead of transferring everything over to the forward spar like on the original 707. In fact, investigators later proved that this design actually worked as Boeing expected. The loads really would redistribute to the middle chord, and the stabilizer wouldn't fail. On top of that, Boeing's analysis also showed that with three chords, the fatigue life of the rear spar would be improved on the 707-300 versus the original 100. So, this all sounds great, right? Well, not exactly. And that's because this wasn't the only change that Boeing made on the 707-300's stabilizer. During flight testing, it was later found that the enlarged stabilizer area caused it to flex more than the original, resulting in some undesirable elevator control characteristics, since the elevators are attached to the back of the stabilizer. To fix this problem, Boeing increased the stiffness of the stabilizer by replacing the inboard part of the stabilizer's top skin with stainless steel instead of aluminum alloy. Now, under the regulations at the time, Boeing was required to demonstrate the fail-safe nature of its new design using analysis or tests. And in this case, Boeing chose analysis based on the testing that had been done on the original 707 stabilizer and calculations of the new load paths. As I said earlier, Boeing's analysis of the stabilizer's behavior of the failure of the top chord attachment were later found to be correct. But, that analysis

assumed that the top chord attachment point was both the most critical failure point and the point that was most likely to fail, since those things were true for the original 707-100. Now, what nobody realized at the time was that the change in the stiffness of the top skin had actually changed the location where the top chord was most likely to fail, making the whole analysis irrelevant. And bear with me here because this is about to get a little bit more complicated. You see, the top skin of the stabilizer is placed in constant tension by the downward aerodynamic bending force during flight. Kind of the way that the skin of the top of your arm gets stretched when you pull on it from below. This tension has to exit via the stabilizer attachment points. So, the load normally passes from the skin into the spars via fasteners and then down through the spars into the attachment. But Boeing's engineers knew that the load on each of the fasteners would not be exactly the same. A higher load on the inboard fasteners closest to the tail was expected because in that area the skin was also attached to the rigid crosswise closure rib at the inboard end of the box structure, making the skin in that area less flexible. And the less flexible the skin is, the greater the load will be that's transferred onward from the skin into the chord via the fasteners. This natural tendency was now further exacerbated by the change in skin material from flexible aluminum to less flexible steel in the inboard area. Now, we know that Boeing anticipated this because the fasteners attaching the inboard part of the top skin to the rear spar top chord on the 707-300 were a steel high shear type designed to withstand greater forces than the aluminum fasteners used further out on the stabilizer. — These high fastener loads were somewhat undesirable, but there wasn't really anything that Boeing could do about it. Now, the best way to reduce stress on the fasteners would have been to make the fasteners larger and thicker. But that couldn't be done because the fasteners were inserted into holes in a flange protruding from the upper surface of the top chord, and the holes couldn't be made bigger without compromising the strength of the flange itself. So, as a result, Boeing's engineers just accepted that the higher stress on the inboard fasteners would be transferred into the top cord, reducing its safe lifespan due to increased metal fatigue, which they saw as an acceptable trade-off because the top cord was fail-safe. But, this change in skin material had been made after the stress analysis on the stabilizer had already been completed, so its consequences were not fully understood. And under the regulations at the time, Boeing wasn't required to determine the safe fatigue life of a structure that was designed using that fail-safe concept. And this meant that Boeing never realized that the stress on the inboard fasteners was actually much higher than they had assumed, meaning that the safe life of the top cord now also became reduced by a lot more than expected. Now, since the fail-safe rear spar was supposed to withstand the failure of the top cord, this oversight shouldn't have been catastrophic. But, it would take 17 years for anyone to realize that this assumption was also wrong. Meanwhile, hundreds of 707-300 and 400 series aircraft were being manufactured in this way, including Gulf Bravo Echo Bravo Papa back in 1963. As these aircraft completed thousands and then tens of thousands of flights, mechanics started to notice warping on the inboard fasteners who were attaching the stabilizer top skin to the rear spar top cord. But then again, fastener distress was fairly common at the time and not always indicative of a serious structural problem. But in this case, the problem was actually pretty serious. You see, over time, the high loads on the inboard fasteners were causing them to warp and elongate their attachment holes and in the process relieving some of the stress that they were under. Now, this sounds really bad, but it this was really kind of a good thing because it meant that less stress was passed on into the top chord. However, it has to be mentioned that the stress on the fasteners was greatest at the inboard edge of the skin and it then progressively decreased with each successive fastener outboard along the top chord. And around the 11th fastener, the load became too low to warp the material, meaning that after that point, 100% of the stress was transferred onward into the top chord. Which in turn meant that the spot where the top chord was most at risk of metal fatigue wasn't the

innermost fastener under the highest load as Boeing had predicted, but actually the 11th fastener outboard. So, on a number of aircraft, including the one in this story, cracks had therefore started to form in the top chord near the 11th fastener, growing slowly longer every time that load was applied to the stabilizer. For many years, this crack on Golf Bravo Echo Bravo Papa's right hand horizontal stabilizer then crawled outward from the fastener hole and across the upper surface of the chord before eventually it started inching downward through the chord's cross section. In theory, this crack should have been caught during regular inspections, but that didn't happen. Likely because Boeing had never expected significant fatigue cracks to form in the top chord itself within the lifetime of the aircraft, since they had underestimated the magnitude by which the addition of that steel skin had shortened its fatigue life. And as a result, the Boeing Maintenance Planning Document or BMPD, used by airlines to design their inspection schedules, only called for a visual inspection of this area during each C check. Now, a C check is a major round of inspections of every part of the aircraft at an interval that depends on the airline and aircraft type. But for Dan-Air 707s, it was every 1,800 flight hours. At each of those C checks, inspectors were supposed to examine the stabilizer's exterior surfaces, rear spar, and hinge fittings, but only those parts that were visible without removing any components. A more significant inspection was called for during very rare intensive structural inspections, but Boeing only recommended performing these checks on a quarter of the fleet every 21,000 flight hours. Now, Dan-Air was conscious that it operated an older fleet and had therefore shortened this interval down to 14,000 hours, but even so, Gulf Bravo Echo Bravo Papa was never among the quarter of the fleet selected for this inspection. And on top of this, the inspection cards used by Dan-Air and other airlines also didn't explicitly call out the rear spar as an area to be given special attention. And the time allotted by the BMPD for the stabilizer inspection was only 24 minutes, meaning that only a cursory visual check was expected to be done. The investigators later found that the type of fatigue cracks that were found on this and other 707-300 aircraft would have been very hard, if not even impossible, to notice with the naked eye, unless the inspector already knew where to look. And therefore, a C check inspection could most likely only have discovered these cracks after the top chord had failed completely, meaning that the fail-safe design would then have had to provide sufficient resistance for the stabilizer to survive with a broken top chord until the next C check. Now, the risk of the fail-safe design concept is that once the primary structural element, in this case the top cord has failed, the safe life of the secondary structure must be greater than the inspection interval. That's while at the same time the strength margin in the secondary structure is usually much less than the original intact structure had been. So, designing a fail-safe structure with an inspection regime that relied on discovery only after the primary failure had occurred was therefore quite difficult to do safely. So, detecting cracks before the primary element actually failed would be much better. But for that to happen in this case, Boeing would have needed to prescribe a much more intensive inspection method than just a 24-minute visual check. In the final report of this accident, investigators wrote that a fail-safe structure is only safe if it meets the following six conditions. First, the secondary structure must withstand the same loads as the intact structure and survive those loads for as long as it's needed in order for the failure to be discovered. Second, the chances of a failure of the primary structure due to fatigue, corrosion, or impact damage must be minimized. Third, adequate access must exist for easy inspection of the primary structure. Fourth, the inspection regime must use methods that are likely to discover a failure. Fifth, airlines must implement the inspection regime correctly. And sixth, the manufacturer must receive continuing feedback about damage or failures observed in service in order to detect any design flaws that might have been missed. But unfortunately, in hindsight, investigators believe that Boeing's fail-safe stabilizer design only fully met the first of those six conditions. And due to the very limited

understanding of structural fatigue back in 1959, the Federal Aviation Administration had accepted Boeing's designs despite these shortcomings since it met the regulatory requirements at that time. And that in turn then meant that C check of the C check had come and gone on this aircraft first at Pan Am and then at Dan Air and the crack had just kept growing until 7,200 flights after the crack had started, the top chord finally failed and the fail-safe design kicked in. And that brings us to the final part of this story. At this point, Gulf Bravo Echo Bravo Papa was, like you can imagine, flying on borrowed time. But the question was, had enough time been borrowed to get this plane to its next C check where the broken chord would surely have been discovered? And to answer that question, I want to go back to something I brought up much earlier in this video, which is Boeing's assumption that a failure of the top chord was both most likely and most critical at the attachment fitting. Now that assumption had been true on the 707-100 and 200 series, but it turns out that it was not the case on the 300 and 400. And that's because, like I explained before, on those, the most likely point of failure was not actually at the attachment but at the 11th outboard fastener. And because Boeing had never considered that, they also hadn't predicted that on the redesigned stabilizer, a failure at this new location was actually more critical than a failure at the attachment point. When the investigators later tested this by cutting the top chord in two at the 11th fastener and then subjecting it to flight loads, they found that instead of the tensile load being transferred to the backup middle cord and its attachment, the remaining inboard 35 cm of the top cord actually continued to carry a portion of that load. Now, that would have been impossible if the failure had happened at the attachment itself, which was why Boeing hadn't anticipated this behavior. But in practical terms, this meant that the downward bending load applied to the stabilizer was then transferred down into the middle cord to go around the break in the top cord, but it was then flowing back up into the remaining stub of the top cord and out through the top attachment point. And that was because, remember, the middle cord attachment point was deliberately left loose so that it would not carry any loads until the top cord was disconnected, which in this case still hadn't happened. Now, as the load traveled upward from the middle cord back towards the top cord attachment fitting, the middle cord was subjected to tension in a vertical direction instead of the lengthwise direction it was designed for. And because that was never supposed to happen, it lacked the capacity to resist. As a result of this, the fatigue crack continued downward from the top cord through the upper web structure and into the middle cord, traveling along the underside of the middle cord's top flange as the flange started to pull away. At this stage, the crack was growing quickly, traveling as far as several centimeters per flight, since the badly damaged structure was now no longer capable of withstanding normal flight loads. Remember, the very cornerstone of the fail-safe concept was that the secondary structure had to withstand normal flight loads for quite a while in order to survive long enough for the primary failure to be detected. But unfortunately, this fail-safe stabilizer design was only fail-safe if the failure happened at the exact point they had chosen to test it, a classic engineering mistake. So, with Golf Bravo Echo Bravo Papa's right horizontal stabilizer on the brink of failure, and the next C check still hundreds of hours away, disaster was now almost inevitable. It was just a matter of when and where it would happen. Back on board this flight over to Lusaka, the poor crew had obviously no way of knowing that the right horizontal stabilizer was now hanging on by a thread. At 11:07 local time in Zambia, the flight contacted Lusaka approach, which cleared them to descend down to 7,000 ft. And at 11:28, the flight crew reported that they had the runway in sight. Lusaka then cleared them for the approach into runway 10, to which the first officer simply replied, "Roger. " And that would be the last transmission ever heard from this aircraft. In the cockpit, the pilots were now busy configuring the aircraft for landing, lowering the landing gear, and extending the flaps towards the landing setting of 50°. And by this point, the plane was also quite light on fuel, and the center of gravity was therefore close to the forward limit, requiring the horizontal stabilizer to produce more downforce to keep the aircraft balanced.

On top of that, extending the flaps was also found to increase the load on the stabilizer, with flaps 50 being the most adverse position. But of course, without any idea of what was about to happen, this crew just placed the flap lever into the flap 50 position as required by their procedures, and with the characteristic hum, the flap actuators then started driving the flaps outward and downward into position. For 25 seconds after that, everything seemed normal. But then, as the load on the horizontal stabilizer reached its peak value, the right-hand stabilizer suddenly just gave way. The crack surged through the remainder of the middle cord and instantly launched down across the lower web and through the lower cord, completely severing the rear spar. This then caused the entire right horizontal stabilizer to be ripped away in just a fraction of a second, which then caused a cascading sequence of secondary damage. The sudden asymmetry in downforce caused the center section of the stabilizer inside of the tail to shear out of its mounting, allowing the intact left stabilizer to sag downward, which in turn wrenched the trim jack screw so hard that it broke, severing all trim control and causing the left stabilizer to become free floating. When the right stabilizer had departed the aircraft, it had pulled the elevator control rods all the way to their full extension, deflecting the elevators fully nose up, which now caused the elevator to act like an aerodynamic lever, forcing the free floating left stabilizer to rotate leading edge up, which corresponded to aircraft nose down. The left stabilizer therefore instantly snapped to 25° in the nose down direction, which was far beyond its design limits, and combined with the loss of half of the stabilizer to begin with, this extreme nose down trim application immediately put the aircraft into a dive — steeper and more sudden than almost any flight crew in history has probably ever experienced. And this meant that the pilots only had time for a few brief panicked shouts as their aircraft now suddenly and without warning plunged forward towards the ground at a height of just 800 ft. The pitch over maneuver was so dramatic that the pitch angle actually surpassed the vertical, reaching -100° in a matter of seconds. Moments later, — the plane slammed almost upside down into a field just short of the runway, still moving forward but with its tail now ahead of the nose and at an angle of attack of -50°. The impact and the ensuing explosion instantly killed all six crew members on board with the airport fire rescue teams witnessing the horrifying crash from the airport. They immediately jumped into their cars and rushed to the scene which they reached in less than 5 minutes, but at that point all they could really do was to extinguish the flames because there was no one left to save. Investigation into the crash led by Britain's Air Accident Investigation Branch at the request of the Zambian authorities proved to be an underappreciated landmark in the evolution of aircraft design standards worldwide. As the findings evolved, the FAA issued three airworthiness directives mandating increasingly thorough inspections of the 707-300 and 400 stabilizers, and during the following inspections it was found that 38 aircraft out of a fleet of 521 indeed had cracks in the rear spar, of which four was so severe that the spar had to be completely replaced. Later, the FAA issued additional airworthiness directives requiring operators to inspect the rear spar top chords of affected 707s every 375 flight cycles. And in 1979, they mandated the addition of a fourth chord to the rear spar in order to make the design actually fail-safe. Even more structural improvements were then mandated 11 years after the crash in 1988 following in-service experience with the initial modifications, but the consequences of this accident stretched far beyond just the Boeing 707. In fact, they led the industry to abandon the fail-safe concept as the preferred method of certifying the safety of aircraft structures. Now, some aerospace engineers had always been skeptical about it, and in the early 1970s the British CAA even imposed a mandatory service life limit on some aircraft certified under the fail-safe concept, with the Dan-Air accident being the real catalyst for this. So, while fail-safe elements are still used in aircraft designs today, the governing design philosophy after 1978 officially became the damage tolerance concept instead. Under that, the inspection intervals and techniques are tailored to the specific

fatigue characteristics of each element in order to detect cracks or damages early before they can lead to the type of obvious failure that was previously relied on. And when certifying critical structures whose failure could be catastrophic, manufacturers are now also required to support their analysis with real-world test evidence. But perhaps the most relevant lesson here is that the use of assumptions about previous designs must be based on a complete understanding of how and why these assumptions were made, and that's something that I think goes way beyond just aviation. Now, if you like technical explanations like this one, but you're also curious about accidents outside of aviation, then make sure you have subscribed to my sister channel, Blackbox, and here comes a recent example. Right. Now, click here if you want to see the full video of that, and remember that you can support the work that we do here by scanning this QR code or by going to patreon. com/join/mentorpilot. You can try that out completely for free, and I would love to see you there for my next hangout. My name is Petter Hörnfeldt, and you're watching Mentor Pilot. Have an absolutely fantastic day, and I'll see you next time. Bye-bye.