The Queen of the Skies

Good afternoon my aeronautics enthusiasts,

After the great feedback I’ve received from my last blog I would like to thank you all for all your support! Every week I try to improve the quality and obviously to make them more entertain and interesting. After 3 weeks watching in class a video about a D-Check of a British Airways Boeing 747-400, I would like to tell you more interesting things about this inspection.

In this video they explained all the process of the inspection since the plane arrive to the hangar and when it leaves it. But wait a moment…. I almost forgot to explain you what a D-Check is!

For understanding a D-check you must know that airplanes have a maintenance plan. It’s almost like the manual maintenance of a car which says how often you need to replace parts or check the condition of it, the same thing happens with planes. When planes are at the hangar it can be because they need a reparation of a broken part caused while being operative or maybe they’re a completing a check. Depending on the check it can be letter A, B, C and D. Depending on the importance, the letter will higher (A to D), the higher the letter the deepest the check. Depending on the number of flown hours or the older gets the plane, the check will be stricter (D-check). After performing the D-check, which is the most exhaustive one, it’s almost like having a fully new plane and the check will start again from A and after the years or flown hours passes a D-check will be performed again. But as you will see later, planes have limited life and when they are to old it is when they get scraped and salvage only important pieces. The cost of maintenance is higher as the plane gets older, so there is a moment where airlines return the plane or scrap them. Even if the structure looks fine, the materials are old and they lose their structural properties. For example, the 747 could fly until the plane is almost 25 years old which is a lot of years!

After this quick explanation of the different checks, we can come back to the video of the B747. In the video the plane is also called by his registration VX (Victor X-Ray), it is 14 years old and it is worth 2 million pounds! That’s a lot of money! 

As it has accumulated 36 million miles which is the equivalent of 1500 times around the world (what a crazy distance!) a D-check must be performed to the plane. As I mentioned before the D-check is the deepest check and they will need to dissemble all the plane. They will need to remove all seats, racks, galleys, bathroom, flaps, slats, engines, cockpit instruments and many more. All of them will need to be checked to ensure that they are safe and in good conditions for continuing working. As you will see, the plane will be stripped out to his aluminium shell for searching any broken wire, any damage or cracks in the structure.

During all the process we’ve seen and learn lots of interesting things and one of them is the number 3. I know that you can’t wait to read about the mysterious number 3 but you will need to wait a little bit, I want you to create some hype for the end. In that way you will red me with more enthusiasm!

As the 747 is a very big plane, almost all the maintenance will need to be at height. Just to know, the tip fin of the tail is at 20 meters above the ground which the equivalent of more and less 7/8 floor in a house. I must admit that forgetting your tools on the ground won’t be very funny once you are upstairs!

Another interesting fact it is that as the front wheel on the nose has no brakes once the plane takes off the wheel spins at very high speed. So, when the nose wheel is retracted there are two big scuffles plates that slow down and stop the tires from spinning. I’ve never thought how the wheels stopped from spinning once the plane took off. That’s a good nice to know!

In addition, we also learn that the autopilot could land the plane but just doing the task of the route. In other words, all the manual levers cannot be activated by the autopilot such as the flaps, landing gear, the reverse and the manual breaks. So, the plane will always need a pilot unless you find an autopilot such like the movie Airplane!. Also related with flight, the black boxes which are actually orange boxes are the one that record all the voices and data at the cockpit. They are protected with thermals packs impregnated with chalk and water and in that way they should withstand 30 min at 1000ºC, which is the temperature that fuel burns. Just imagine being at the sun at 40ºC for 10 min. You will be already toasted and sweaty, so imagine being 30 min at 1000ºC. What a hot day! 

Another amazing feature is related with the engines. When the plane is fully loaded it needs approximately a 120.000 Horsepower from its four engines to get into the air, which is the same as a thousand of family cars pulling the plane. Each engine works like a big vacuum machine that can aspirate in each the second the same amount of air contained in the volume of a telephone red box! All this power is also possible thanks to the fuel and the total capacity of all the 8 fuel tanks that has the 747 is 216.000 L. With all this fuel you could fill approximately 3.000 cars, can you imagine the total fuel that is used in all the planes around the world?

Finally, before starting with the mysterious number 3 I would like to tell one more amazing fact about the plane. When all the fuselage is stripped out, you can see all the cables around the plane and in the video they said that the total distance of all the wiring system was about 172 miles which Is the equivalent of 276 km. I live in Mallorca and the distance between the tips of the island is 100 km so with all the wires of the 747 we could go to the opposite tip and come back again!

Don’t worry guys, number 3 is coming right now!! 

This number is related in many fields of the plane, one of the first time we learn about number 3 was that 3 seconds is the time necessary to deploy an emergency ramp for evacuate the plane. I must say that as I’m an air hostess I already knew that fact of the plane! The problem comes when all the 30 square meter (another 3) of the ramp need to be folded precisely back in his container which is only half square meter! All the process of folding takes a total of 6 hours which is ridiculously high compared to the 3 seconds for deploying it.

Another feature is the number of hours that a D-check needs to be performed which is more than 30.000 hours to complete the full check. Just for a moment try to think how many years all these hours are. Did you get it? Yes, it is almost 4 years, but this is the total hours that add up all the 200 workers on the D-check, that’s why the plane is only 5 weeks at the hangar. All these 30.000 hours are distributed in more than 12.000 tasks that must be done in the plane. The hangar is fully operative all 24 hours a day! As you can see there is a lot of work to do on the plane and try to think in all the planes that a company has. The bigger the company, they will have more planes and depending on the size of the planes they’ll need a lot of hangars and most importantly lots of mechanics to perform the tasks. 

Last but not least, another important fact with the number 3 is related with the salvage parts. An old main landing gear of a 747-400 costs around 300.000 dollars and this is just one of the sides of the main landing gear without wheels! As you can see plane parts are awfully expensive even the old parts, so imagine buying new ones! Another price with a 3 is the price of a single window of the cockpit whose cost is around the 30.000 dollars. As you can see a single window of a plane costs the same as a brand-new car.

For the moment this is my largest blog and I hope to have resumed all the important parts of the D-check on the Boeing 747-400. It’s a lot of info but has always I tried to make it the most interesting as possibly. Watching this video made to increase my enthusiasm for start working at the hangar. I know there is a long way left but I will try to give the best of me for achieving this objective. Next week more info as always. Hope you’re having great days even with this virus outside!

See you on next week folks!