Mission Aviation Fellowship

8.33kHz Radio Concerns

Report Text: This is not an incident report but a general observation in response to a number of reports of 8.33 radios being operated incorrectly.

My club has three aircraft and as a result of EU rulemaking we now have five different radios in the fleet and two different transponders. The new radios are significantly more difficult to operate than their predecessors. Some have a system where the rotary knob changes all three decimals, some require a cursor to be slid sideways before the digit or group of digits can be changed.

On one the volume control is so close to the C/N switch (I leave you to guess what that is) that it is impossible to adjust the volume without changing the C/N display. One has a volume knob which, if inadvertently pressed for a couple of seconds while adjusting it, switches the radio off.

Some have the old-fashioned squelch lift test button, others do not. The new Mode S transponder also requires significantly more switch selections and button presses than its predecessor. Meanwhile our local controllers have devised procedures which often require three or even four simultaneous squawk and frequency changes in the space of about seven minutes.

I doubt that there are ANY ground stations within 200 miles of where I fly which have an adjacent frequency separated by less than 25kHz. The makers of these avionics have, it seems, never been in an aeroplane. The constant fiddling with frequencies and squawks has completely replaced lookout as a cockpit activity.

We could, I suppose, ‘stud’ the sets [pre-tune frequently used frequencies into easily dialled studs or buttons] but students will eventually have to learn to operate the sets manually.

Oh for the 10 channel VHF box we used to have in the Chipmunk! Oh for the simplicity of the ARC 52 in the jets of the 1950s and 60s. These new pieces of kit have been designed by non-flyers, which is perhaps why the Mode S transponder has a ‘VFR’ button which selects 7000. Since when did 7000 mean VFR in this country? I could go on.

On my once a year night flight on my own, in the dark, all by myself, over featureless terrain, I found that maintaining a scan while selecting a new (and unexpected) frequency and at the same time dialling up a new squawk was all but impossible.

CHIRP Comment: Cockpit ergonomic issues are as old as aviation and in this area of Human Factors it seems not all developments are positive. Many items of modern avionics leave much to be desired in terms of ergonomics. As frustrating an issue as this is, it is still a known one and therefore it can be addressed.

Aircraft owners who have the option to choose their avionic equipment should consider the ergonomics and not just the functionality. However, pilots hiring aircraft from flying clubs have little choice over the equipment installed in a hired aircraft and possibly limited opportunity to familiarise themselves with it before flight. The AIWG [Airspace Infringement Working Group – Ed] has identified lack of familiarity with equipment as a significant factor in own-aircraft and hired-aircraft infringements.

It is clear, therefore, that all pilots should make every effort to familiarise themselves with the aircraft equipment before flight, including using interactive websites where these are available for specific items of equipment.

With regards to Mode S transponders, readers will be interested to learn that some ATC Units allocate the same squawk to several different aircraft in the same area and use the Mode S Flight Identification facility to identify each individual aircraft. This explains why you may hear your squawk being allocated to other aircraft.

From a ‘GA CHIRP’ report

Author: FTN Editor

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