Budget airline cartoon

Your Letters

Send your letters to The Editor, E&T, Michael Faraday House, Six Hills Way, Stevenage, Herts SG1 2AY, UK, or to engtechletters@theiet.org. We reserve the right to edit letters and to use submissions in any other format.

Cities aren't just for drivers

The focus on smart cities in the June 2016 issue of E&T overemphasised motoring technology, featuring systems to park your car, pay for parking, manage vehicular movement and avoid vehicular traffic build up. These are indeed all beneficial developments, assuming of course that one is in a vehicle in the first place.

It’s right up there with environmentally friendly tram systems or hybrid vehicles. What exactly is environmentally friendly about any energy-consuming vehicle? Carbon fuels still power the vehicles and the power stations (which feed the trams), with nuclear backing it up and the occasional bit of alternative power, on a good day.

The smart move of course is to get out and walk. Or cycle. It is free, uses no carbon fuel, and improves the nation’s health. Yet there is little technology – or legislation – focused worldwide on this form of green energy and healthy living. There is an established assumption that vehicular movement is the problem, and therefore we need to improve the life of the vehicle. Tax breaks for footwear? Grants for bikes? No. But there are tax breaks for certain vehicles. Priority for pedestrians at road junctions? No, but there is software to manage traffic lights for trams and vehicles.

The smartest thing to do to a mechanically propelled vehicle in a city is to stop it immediately. The smartest way to do this is to focus on getting people into the right place, without the vehicle. A smart city would have its workers living within walking distance of their workplace, school or entertainment zone.

From the very early days of computing we have been taught that if your system is a mess in the first place, computerising it will only create a computerised mess. We need to fix the cities first, before we computerise them. Now that would be smart.

Charles Dunn CEng MIET

Retrieving flight data

Am I the only one to suspect that the problems of more timely retrieval of information from flight data recorders (‘Why Are Flight Data Recorders so Hard to Find?’, July 2016), are being made out to be greater than should be expected?

I take the point about the inherent need for conservatism in aircraft systems design, but fail to see why it would be a big issue to equip at least long-haul aircraft with continuous telemetry. The data rates being talked about as if they were very high seem on investigation to be nothing of the sort.

I understand that the very latest specification for FDRs requires them to record 256 12-bit words per second – i.e. a little over 3kbit/s. Maybe double that with high levels of error-correction coding and other overheads. That is about a fifth of the data rate of a single GSM 2G mobile phone handset and a twentieth that of a typical bit of streaming audio or MP3 file.

Some European airlines already permit in-flight use of mobile phones, the US has two bands set aside for communication with in-aircraft picocells to allow phones to be used, and the ocean areas are served by constellations of communication satellites, so just how hard could it be for that data to be streamed in real time? Even easier if a critical subset with maybe a tenth the bandwidth were on continuous stream, with the data rate boosted in the event of apparent extreme circumstances.

It seems to me the industry should concentrate on getting that into place quickly rather than divert energies to halfway houses such as last-minute transmission, which would in any event need most of the same infrastructure to be in place.

Alex Gray MIET

Since the loss of Malaysia Airlines Flight 370 I couldn’t understand why the flight recorders had to go down with the plane, but having read your article I started to think more about this.

When a plane sinks to just 70 metres the water pressure is about 7 bar, which should easily be enough to compress a diaphragm similar in principle to an aneroid barometer. This movement could trigger an ejector mechanism using a propellant similar to a car safety bag. The recorder then floats to the surface away from the tangled wreckage on the sea bed. Using GPS the last known position of the aircraft will be stored in the recorder.

Tim Bradbury CEng MIET
By email

Over 15 years ago, while I was working for Sonardyne International, we pointed out that our acoustic transponders were often deployed onto the seabed months or even years before they would be required for use. Transponders use very little power listening for commands. So the batteries last for years. It is the transmission of signals that consumes the power. Instead of using beacons that shout whether there is anyone to listen or not, it would be much more sensible to conserve the power for when someone calls and listens.

Another advantage is that by measuring the time between the transmission of an interrogation from three places and the receipt of a reply, it is possible to pinpoint the location of the transponder much more easily than finding the position of a beacon .This is technology that has been available for decades and I fail to see why it has not been adopted.

Antony Wakeling CEng MIET

Pollution control sceptic

Am I alone in doubting the merits of Audi’s new ‘flow transformer’? The application involves the inference of flow from change in temperature as measured by a temperature sensor in the air intake. Audi claims that measurement accuracy (and subsequently pollution controls) can be improved by inserting what can only be described as a perforated plant pot into the intake upstream of the sensor. I sincerely doubt it. I also suspect that the net impact on pollution of the planet, bearing in mind that the device is made of plastic, will be negative.

Robert J Howie CEng MIET
By email

Sales sterotype

Jack’s Blog can do better than recycling the myth that engineers and sales teams are different species, with the implication that ‘real engineers’ are only the ones in the company’s design and development jobs. The best engineering sales people are engineers. It’s perhaps a pity though that the converse isn’t true – the best engineers are still reluctant to go into sales, maybe discouraged by these stereotypes.

Chris Cheek CEng MIET
By email

Gap in wave power story

Wave energy is in an area very close to my heart, having worked in the field at the beginning of my career, and I was disappointed that the project I was involved with – Wavegen’s LIMPET – did not get any mention in your article ‘Harnessing the Waves’ (July 2016).

This project was, we believed, the first grid-connected wave energy machine at a commercial scale and happened in 2000, four years prior to the Pelamis device mentioned in your article. Sadly Wavegen has gone the same way as the two other big Scottish wave power companies you mention. The work of Wavegen and Queens University Belfast along with Salter and University of Edinburgh all played a part in progressing the wave-energy industry and enhancing our understanding of the challenges of this technology, which have yet to be solved at an affordable level.

I understand the article was not claiming to be a historical summary of the wave energy industry but I hope there is some way to correct this error as I am immensely proud of what was achieved in 2000.

Hamish Ellen CEng MIET

Loose threads?

I was intrigued by the front cover of this month’s E&T. What is the significance of and how many other engineers have noticed that the bolt shown on the cover has a left-hand thread?

Paul Hawkins MIET
By email


Recent reports about interstellar travel using micro spacecraft remind me of a cartoon showing two cave men looking at equations they have written on the cave wall, and one says “...but we don’t have the technology”.

Richard Riggs MIET

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