Comments by "Keit Hammleter" (@keithammleter3824) on "Mentour Now!" channel.

You get this situation in any technical field. I used to do TV repair. Any one of a hundred parts could cause loss of sound. As far as the customer is concerned its the same fault every time. What you do is build in a bit extra in your standard pricing, so that when luck brings you back to the same customer with the same symptom(s), you can fix it for free and retain the good will. You cannot expect customers to understand technical detail. When you fix faults you should also do basic checks that usually will reduce the probability of a callback. My car was leaking coolant, so I took it to the dealer. The mechanics spotted that a hose was weak so they replaced it. But next day it still leaked coolant. This time they identified another dodgy hose. They considered that a separate fault and wanted to charge me full parts and labour again. My view was that if they were competent, once they found one dodgy hose, they should have checked ALL hoses - after all they were all equally old. So I offered to pay for the extra part cost but not the extra labour, as the labour in the first job I had already paid for turned out to be not properly done. I had to fight for that one though. But if it was coolant leak problem and next day a brake fault, then clearly the faults are unrelated and the customer should pay for two different lots of parts and labour in full.
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If you ask if the TU-144 came about due to espionage, you are asking the wrong question. If you think it was for propaganda reasons, you need to think further. What is the value of being seen as a cheating copycat? Not a lot. A Russian guy gave me an explanation that makes complete sense. In the 1930's, the USSR had put a lot of funds and effort into training their best and brightest as engineers, and spent a lot of scarce cash importing western machine tools and laboratory instruments. But the products of Soviet industry often remained well behind the technology in western factory products. But because their products looked and worked very different to western products, non-technical top officials like Stalin had trouble evaluating whether Soviet designers had done a good job or not - and the reasonable suspicion was that they hadn't. Stalin tried making an example of some designers and programme leaders by sending them to Siberia, but that didn't work. In the late 30's Stalin got fed up and put in place a new policy. Every time the West came up with something new, Stalin and his execs told Soviet industry ""I want something just like that. Not a different product. Something the same." This was Stalin's way of forcing the designers and engineers to catch up and prove that they had caught up. So when they got hold of Studebaker trucks they copied them. When 3 B-29 bombers ran low of fuel over Japan and had to land in the USSR, they copied the B-29. As the USSR was metric and everything in the B-29 non-metric, It would have been cheaper to design their own intercontinental bomber. When Stalin wanted a new limousine, they got hold of a US-built Packard and made one just like it. It would have been cheaper to design their own limo, as the Chinese did for Mao. It didn't matter whether they copied from a sample, or used spies to get copies of drawings, or worked it all out themselves. What was important was that they followed orders and came up with the same thing. It wasn't super important that the USSR had a business case that would stand up. If there was a clear need for something unique, they usually produced something unique, like radios that ran on kerosene for use by nomadic tribes in remote Mongolia. But because radios that ran on kerosene wouldn't sell in the West due to batteries being readily available and kero not used for heating and lighting in one's yurt, it didn't mean anything to Soviet top leadership. Stalin died, but the policy remained in place right up to Gorbachev's time. That's why, when the US came up with the Dynasoar space plane, the USSR built one. When the USA built space shuttles the USSR built a few. Whether they needed them or not. That's why they built the TU-144 - still following the policy set by Stalin that Soviet engineers must continually clearly prove they can do what western engineers can do. The USSR was just a big government department. Government departments the world over, once they set a policy in place, it is awful hard to cancel it. No official wants to take a risk inherent in change. The Russian Dynasoar, the Russian shuttle, and the TU-144 - they were all a waste of money. That didn't matter. What mattered is that they proved to Soviet top leaders that they could do it. That's strategically important. If a Khruschev or a Breshnev sees a Concorde and he sees a Concordski, he's happy, and doesn't need to demote someone. It doesn't much matter if it proves unfit to carry passengers. They can fly on the regular planes.
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No, they were not. At one stage they were about the 5th. Google and see. However they had developed a method of refining the metal using monstrous vacuum chambers that was cheaper than Western methods.
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The Royal Australian Navy (RAN) acquired a war surplus WW2-built British aircraft carrier which they called Melbourne. They kept it operational until 1982. It was mend and make do the whole time. Partly because parts were not available, partly because the RAN couldn't afford to do things right, and partly because it was junk when they first got it. But nothing nasty happened, not due to mend and make do anyway. It did run over and sink a RAN destroyer - but that was because of a signalling code error. It also ran over and sank a USN destroyer but that was because the USN commander was incompetent.
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If I ever become a squillionaire or the dictator of a major country, stuff it, I'll just get the biggest most expensive plane my peasants can cough up. Meanwhile, as an ordinary engineer .....
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@phonicwheel933 In your first sentence, you've got it in one. FMEA lets you see safety deficiencies BEFORE they cause accidents. Re ADF windows,, I'm speculating here - since I don't have access to DeHavilland records - but since the ADF antenna and it's electrically insulating surround was supplied to DeHavilland by their usual supplier, it would have been the supplier's responsibility to design it to cope with presurisation and largely the supplier's responsibility to test it against presurisation. But DeHavilland didn't tell them it was for a pressurised aircraft - that was the problem. However, DeHavilland should have at least audited the supplier's records to discover and verify whatever testing was done, given any hull penetration is flight critical. I guess they didn't.
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Post 3: At 21:10, Mentour Now talks about what the aircraft industry owes to the Comet - the good that came out of the Comet disasters. He talked about teaching the industry the need for failsafe systems and robust fatigue testing. Well, the need for failsafe systems was already known, just maybe not in DeHavilland. The formal engineering discipline for achieving fail safe systems in FMEA (Failure Mode Effects Analysis) which was well established in the industry, particularly in the USA. FMEA as a critically important discipline was established during WW2, when aircraft engineers needed to ensure that military aircraft did not crash unless shot at, and that aircraft should survive being shot at to the maximum degree feasible. Metal fatigue was also understood, since all metal aircraft go back to before WW2. Just not well understood within DeHavilland. Here we see the result in poor quality journalism again, originating falsehood just like they did with "square" windows. It was reported early in the Comet crash history that the stress on the Comet skin in places exceeded the limit for the alloy used. However the limit then, which was somewhat of a DeHavilland engineering guesstimate, was actually stricter than later knowledge showed it needed to be. The real benefit of the Comet was two things:- a) it showed the British certification authority that they needed to do more than just rubber-stamp whatever the manufacturers gave them; b) It really shook up British aviation accident investigation authority - showed them forcibly that they needed to lift their game. The purpose of accident/incident investigations is not to lay blame, it is to find a system or process cause so the industry can eliminate that cause so it won't happen again. When a Comet 1 takeoff incident occurred, the Accident Investigation blamed the pilot. When it happened again they again blamed the pilot. Blaming pilots is a cop-out that solves nothing and achieves nothing. Later they realised the incidents occurred due to aerodynamic problems and was not the pilot's fault at all. I have sat on incident inquiry panels myself (not in the aircraft industry). You always ask what could have happened APART from an operator error. Even if you are certain that it was operator error, you have to ask WHY did the operator err? Was it a training deficiency, recruitment failing, instruments misleading, etc. 99/100 there is a reason, and if there isn't, the process tells you what was wrong with the structure or system.
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Post 2: Mr Mentour Now got my attention at 7:07 when he asked why did the Comet 1 have presurisation problems while other aircraft already in service did not. He startled me at 10:01 when he claimed that the higher altitude of the Comet 1 "meant a much higher pressure differential". That's not right. A rule of thumb applies: air pressure halves for each 5000 metres of added altitude. But since it is the pressure difference between inside the cabin and the outside that matters, not the absolute pressure, we should calculate what the difference in precent is, taking the edge of space (zero pressure) as 100%. it is common for aircraft to not be pressurised to sea level pressure - this saves a little bit of weight. Civil aviation rules require a maximum cabin equivalent altitude of 2400 metres, but various aircraft have been designed for 1500 and 2000 metres cabin equivalent altitude. Here is the data for an aircraft pressurised for sea level and for 2000 m:- Altitude metres % difference cabin sea level % difference cabin at 2000 m 0 0% - 5,000 47 31 10,000 (33,000 feet) 75 67 15,000 (49,000 feet) 89 84 20,000 95 94 We see that the airframe stress goes up but certainly not a MUCH greater amount at the Comet's higher altitude - it's a modest approximately 20% more stress. In any case, there was nothing new that the engineers had to figure out or learn to design for that 20% increase - it was merely a matter of doing the established calculations with the correct data. As Mentour Pilot said, pressurised airliners go back 10 years before the Comet. Use a few more rivets, maybe a slightly thicker sheet for the skin. So, the question is: Why did Dehavilland get it wrong? Answer: Because they had no relevant experience in the company. Unlike the other manufacturers, they had no high altitude transport experience - they didn't realise its not sufficient to calculate skin stresses. You have to tell subcontractors things like radio antenna need to be designed for pressurisation too. They didn't. Dehavilland engineers in designing an all-metal high altitude airliner were like a cardiac surgeon doing brain surgery - yeah, he knows the essential basic principles, but he is not likely to get a good result. It has long been established practice in the American aircraft industry - conduct Failure Mode Effects Analysis (FMEA) - this is a formal engineering discipline that ensures any likely failure will not be catastrophic or kill people. Essentially, they look at each component, identify how it can fail, and if it does, what that will lead to. As in "suppose the glue on the radio antenna fails? Oh, it will lead to skin rupture - that will cause hull failure. Right, we better fix that." Clearly, Dehavilland's engineers did not do an FMEA on the Comet 1, or if they did, they took shortcuts
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@grizzomble : Remember the American WW2 bomber the B29? Three on Japan bombing missions were forced to land in the USSR. The Soviets seized them. They stripped one down completely, used one to test fly and train on, and the third was used to test Russian made prototype assemblies such as engines. Stalin ordered that B29 copies be put into production. This was done and it involved setting up a complete non-metric manufacturing chain to, for example, make aluminium alloy sheets to US alloy specifications and non-metric gauges. They succeeded in making nearly 900 B-29 copies (as the TU-4). But the setting up of non-metric manufacturing of almost everything, involving about 900 parts factories, must have cost a fortune - it was done on an urgent basis on Stalin's orders but it would have been cheaper and quicker to design and engineer their own high altitude large bomber.
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Post 1: Mentour Now stated that "engine access was said to be satisfactory". All of us engineers and technicians who have worked on British and American equipment know what "satisfactory' means when it is said by a British manufacturer. It means the access is difficult and/or requires the undoing of a stupendous number of bolts and/or disconnection of systems.
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For a non-electronics engineer, Petter's presentation is fairly good. Some things need clarifying:- This issue is not really about two government agencies fighting with each other. It is about both agencies not having done their job properly before the manure hit the blades. What should have happened is that there should have been a specification on radio altimeters that set allowable limits on cross-modulation and susceptance (or masking as Petter calls it). The FAA and the FCC should have enforced this years ago. Then, when this issue cropped up, a competent engineer could definitively say yes it will be a problem or no it won't. It is the FAA's job to ensure air travel safety - by getting technical where necessary. It is the FCC's job to ensure various radio and non-radio emitting systems of ANY sort are electromagnetically compatible, and anticipating any problem - a job they have actually been doing for the last 90 years or so. For some reason they let this one slip past. It's worth saying that to a radio/electronics engineer, 220 MHz spacing at 4 GHz is actually a VERY wide spacing - trivial to design circuits that cope with it. At a cost of maybe a dollar (retrofitting is another matter). It is a spacing of ~5%. Compare that with FM broadcasting - channel spacing 150 KHz at 100 MHZ - about 0.15%. Or naval HF comms radio, where receivers must operate within 10 KHz of a high power HF transmitter of the same ship - a spacing of 0.00004%. Let's make this perfectly clear: Its not the 5G manufacturers or the phone companies at fault. The blame lies mostly with the FCC, but to some extent with the FAA and perhaps the radio altimeter manufacturers, if they didn't spend the dollar I mentioned above. (this might actually be a non-problem if they did in fact spend the dollar) No way should it take 2 years to do tests to verify the problem. To an electronics engineer, its simple. If it is going to take 2 years, that's because nobody want to spend any money. There are urban myths about why using mobile phones onboard aircraft are not permitted. It's not all about interference to aircraft systems, as the antennas are outside the skin. Mobile phones work this way: The maximum output is about half a watt, but to conserve battery energy they throttle back their output to just that necessary to reach the nearest tower. They do that by measuring the level from the tower. If its low, they send high, if its high they send low. Now an aircraft is a metal cylinder - it blocks radio waves. And it flies at high altitude, away from the cell tower beaming directions (essentially horizontal). If 300 passengers turn on their phones during cruise, 300 phones are going to emit full power to tray and reach a tower, so the collective power is 150 watts. And due to the metal skin, it can't easily get out. So you are all sitting in a rather weak microwave oven for the duration of the flight. (cf typical oven - 500 watts for a minute or so, but only one lump of food to cook). You know, if you read instruction manuals, that you should not operate an oven if the door seal is damaged, as then a tiny bit of energy leaks out.
1
News journos often get things wrong. We are used to it. Newspaper editors often write wrong headlines - you read the whole article and at the end you realise the headline doesn't match the story. We are used to that too. To be fair, it can be darn hard to write concisely in words anybody can understand (generally, newspapers are written so that any 12-year old can easily comprehend it) without simplifying to the point of misleading - especially when you have a deadline to meet.
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@flagmichael : In any case, if current flowed when the switch was on, current in a return wire would cancel the magnetic field from the hot wire and you would still have no effect on the compass.
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Mentour now said the magneto switches are in the up-high position so they can be seen by crew outside on the ground, so they know an engine cannot fire while they are manually swinging the props. That seems a good idea. But - Other piston engine airliners had the mag switches in the same place (eg DC6) or in other places (eg Ford Trimotor), and the switches are not easily seen by ground crew (in DC6, cabin too high and switches are tiny, Trimotor has mag switches below windows). But this pattern always seems to hold: Engine controls normally used during flight (eg throttles, mixtures, prop pitch) are grouped in one place and easy to hand, and any engine controls normally used on the ground (eg mag switches, generator switches) are grouped in a place well away from in-flight controls - and thus necessarily in a less convenient to hand place. In flight engine controls have distinctive shapes and also move forward/back, but controls used on the ground move left/right or up/down. That all seems very sensible - makes for an easy to fly aircraft - and very unlikely a pilot would accidentally, say, turn off magnetos when he meant to alter mixtures - which would be rather a nuisance and upset the passengers.
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@bazza2540 : Deadly to its' own side perhaps, but the accidents were not due to any failure of its equipment and not the fault of any of its officers and crew.
1