You could set it to zero on the ground or to the airfield elevation - there was no subscale. Once above transition we could set it to SPS.
How do you do that without a subscale?
so the attraction of a 300 foot per mile system was clear.
It doesn't matter whether you use QNH, QFE or bouncing pingpong balls, the glideslope is still the same.
I received my Green Card on Vampires in 1961. I flew my first precision approach (ILS) in 1962. I flew my last as a commander of a public transport aircraft in December 2008 so I have been around a bit.
In the RAF the rules were simple, you flew QFE to the ground. Early on in civil life the situation was much the same until the ninties when you had a choice between of ploughing through the murk on either QFE or QNH. Then it stopped. The civil world was on QNH.
Apart from my company. A major helicopter operator in Aberdeen. Their ops manual said QFE, their simulator demanded QFE and in sympathy with their policy of using pounds instead of kilos like the rest of the world we had to request the QFE before initiating an ILS. Fortunately the operation was fairly parochial so you did not get into trouble elsewhere.
Move forward a few years and then come to Australia, China and the South Pacific. Same company, same ops manual. QFE was binned in Oz and Guadalcanal as being typical Pommie rubbish but not in China.
Step forward British captains and Chinese co-pilots in a country where ther are two settings. 1013.2 in a promulmgated airway or airfield QNH entering or leaving an airfield. We were different. We had a QFE setting in a clutch of airfields including Hong Kong, Shenzhen, Guangzhou and Macao. The new Chinese pilots were somewhat mystified about this, with good reason. BUT IT SAYS SO IN THE OPS MANUAL. You had to hand it to the Shenzhen controllers, though. They would get you QFE for you, come what may, normally just after you had passed the MAP. Eventually, but it took a change of managing pilot, the QFE requiremnt was binned and we entered the world of internationally accepted flying procedures.
So it is with some surprise that I discovered this thread. I am even more surprised that people are defending the status quo. I can understand where countries retain heights and flight levels in metres because they ALL do it in that country. Standardisation is the name of the game so all airfields in the UK should use the same common pressure setting, airfield QNH.
Those dreamers going on about radar and GPS altimeters, forget it. Should you make a 100% reliable radar or GPS altimeter that first time that there is a prang there will be lorryloads of litigation lawyers hammering at your door.