The underlying history of LCY focussed on noise. The airport’s initial approval was based on the DHC-7 aircraft which had been ‘certificated’ (FAR 121 approved) for steep approaches under a US/Canadian ‘STOL’ category, which for straight in IFR approach and landing was 7.5 deg.
The subsequent airport expansion to enable BAe146 jet operations had to consider docklands developments and planning in the surrounding area. The BAe146 was expected to be certificated for a 6 deg approach based on the Canadian ‘STOL’ requirements (Flight Working Paper 705?), which would be acceptable to the UK CAA for commercial aircraft. This work was the basis for the JAA/EASA CS 25 steep approach requirements.
BAe proposed the use a 5.5 deg GS; this provided wiggle room in certification and insurance against the final obstacle clearances.
The obstacles to the west were the planned / commenced building of Canary Warf and existing docklands structures, and to the east the proposed “East London River Crossing” (ELRC) bridge over the Thames which would impact the 27 approach path 1.5-2.0 nm out (400ft towers?).
Complex negotiations involving airport planning, building regulation, and noise enabled a compromise solution. This involved adjusting the already displaced thresholds of the existing runway inwards to enable a 5.5 deg ‘Cat2’ ILS and PAPI which would meet a lower margin obstacle clearance over the near-in dockland buildings and cranes, also a compromise in the height of Canary Warf and ELRC; a senior BAe executive took tea with Mrs ‘T’ who ‘was able’ to reduce the tower height by 1 story – London/UK economic development.
To the east, the bridge was redesigned / realigned so that the dominant obstacles were the reduce-height lampposts and a London double-decker bus; this allowed a similar 5.5 deg approach to a revised threshold.
A further limiting factor was the usable runway length which could not exceed 1199m so to qualify as a code 2 runway; this involved the side-line proximity to water and the obstacle clearance slope over the terminal buildings/parking (BAe146 fin height).
Canary Warf was duly ‘modified’, the other docklands buildings and cranes removed, thresholds displaced, and the ELRC became a figment of political planning providing the steep approach satisfied the then active anti-noise lobby.
The rest is history, probably resulting in local building expansion up to the 5.5 obstacle clearance limit, and thus the near-in obstacles, the small bridges at each end now dominate.