The failings of a two-sensor MCAS system
"I’m writing about the recent Boeing 737 Max problems. In 1966, I attended a lecture in Southampton when a Hawker Siddeley Trident was shown landing at Heathrow in thick fog. The BEA Trident fleet was fitted with the Smiths Industries Triplex Instrument Landing System, which used three independent systems on the basis that, if one was defective, the other two were probably true.
"It is therefore troubling, to say the least, to learn that the Boeing 737 Max uses only two sensors in its MCAS system. As Boeing engineers must have known the implications of using a two-sensor system, why did they go down this route? Was it cost or overconfidence?
"As an aside, the only problem with the demonstrated Trident test was that, once the plane came to rest, the pilot had no idea where to go due to the fog. So a van with a flashing light had to go out and find the plane and guide it to the terminal.
"By the way, your reference to Concorde rudders delaminating because of water ingress through the rivets was incorrect – it was paint stripper, not water (“Remembering Concorde,” Professional Engineering No 1, 2019)."
Professor Bob Adams, Oxford
"Geoff Bell doesn’t need to worry about the heat released by Hinkley Point C or by any other thermal power process (Your Voice, Professional Engineering No 2, 2019). The solar radiation reaching the Earth’s surface is about 780 million TWh per year. In 2015, the global total primary energy supply was 160,000TWh, or just under two hours of solar energy, an insignificant figure that is lost in the noise of the daily heating and cooling cycle.
"As for moving to a completely renewable energy system, moving space heating and most transport to electric power and using a synthetic fuel for those operations that aren’t amenable to electrification is going to dramatically increase our total electricity demand, which will require much of the countryside and coastal waters being dedicated to wind turbines and solar panels.
"We might get away with locating solar power in the Sahara desert (good luck with keeping that secure, with Boko Haram and others in the area), but it doesn’t really fit with our recent national desire to Take Back Control if our main source of power is located several thousand kilometres away on another continent!
"It will probably be found that the most economical and secure source of energy is a mix of renewables and generation three and four nuclear power. But I do agree that it will need the political balls to change our present system. Particularly in the 12 years the climate scientists are suggesting."
Robin Trow, Snodland, Kent
'Flying' land speed vehicles
"As an older member of the IMechE, I have been intrigued for some time by the Bloodhound project.
"Land speed records were made and broken for many years by vehicles powered by devices that caused the wheels in contact with the ground to revolve, and hence cause the vehicle to move. These were truly land vehicles, and the spin-offs had an effect on the prevailing vehicle industry, particularly suspension and tyres.
"The current ‘land speed’ devices are more akin to very low-flying aircraft, with all the forward force produced by a rocket. The only purpose for the wheels appears to be to support the minimal net ‘download’, which might allow the vehicle to fly. What relevance is there to industry?
"Or am I a Luddite?
"By the way, I think the new-style magazine is brilliant."
"Concorde was probably one of the greatest engineering achievements of last century.
"When I saw that this magazine was covering the 50th anniversary, I looked forward to some interesting technical information about how engineers developed it into a superb aircraft (“Remembering Concorde,” Professional Engineering No 1, 2019).
"However, all I read was a list of problems. Considering how advanced it was, Concorde seems to have worked very well. Other, subsonic aircraft of the time had big trouble, like the DC10, and even Boeing’s successful 737 has suffered various concerns.
"Surely we should expect a balanced report that celebrates the feats of the engineers?"
Richard David, King's Lynn, Norfolk
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.