What engine parameters were monitored to provide this indication and how was this done ?
Each engine had associated with it a set of lights , Blue, Amber, and Green
BLUE reverse light --- this reflected the correct operation of the
reverse thrust.
Flashing, rev selected but buckets in transit
On steady reverse selected and achieved
Amber Configuration
[CON] light----------- ON if reheat fails with no loss of engine RPM
On if reverse selected and primary nozzle greater
than 15%
Green Go light---------- This light monitored the engine for correct power
for take-off in that
Fuel flow and P7 had to match or exceed a pre
calculated figures, which were preset on their
individual gauges prior to take off.
The secondary nozzles had to within their
take-off limits
The CON light is off
In the case of No 4 engine the N1 limiter has
returned to normal position
Now normally there was a call of 100kts and at that point there had to be 4 green GO lights illuminated otherwise the t/off would be aborted. There was a concession to this in that if runway/ conditions /weight allowed the takeoff could continue with only 3 green lights illuminated at 100 kts as long as the
affected basic engine was OK[ this covered the loss of one reheat]
The green lights were considered necessary if the aircraft was using a rough runway and nose nodding could interfer with correct engine instruement monitoring and were also handy as the pilots could at a glance check whether they had at least minimum eng power for t/off.
To keep things simply their use was standard on all T/offs rough or otherwise