Can someone tell me how the fan speed is measured on an aircraft gas turbine engine?

Question

Can someone tell me how the fan speed is measured on an aircraft gas turbine engine?

Answer 1

it will be a % of nh or nf depending on where the tacho in the engine is fed from

Answer 2

An airspeed indicator.

Answer 3

I'm not sure what you are asking. In the cockpit it is measured in %

Answer 4

As percent of N1, N2 is the compressor section.

Not sure how 100% is decided as a design limit, as most will have a redline somewhere above 100%; seen as high as 104%.

Answer 5

fan speed is measured by an N1 speed alternator (tachometer) usually when you open a CFM engine (737-300 CF56B1 -800NG-CF56-B7) or any A320 CF56C2 engine or A340 CF56-C5, the N1 alternator/tachometer is connected just aft of the nose cowl firewall.

as i submit this i saw John B answer now i must use my cheat, he is right, it is commonly called N1 speed Tach. gen.

I trust him so I will lock my answer.

Answer 6

Tach generator from the N1 gearbox. Most of em anyway but you didn't name the engine. N2 shaft speed is taken similarly. In it's easiest form, a tach generator is spun by a shaft or gear related to what you want to measure and it then generates a voltage. The faster it spins the more volts and the higher the voltmeter reads. Only instead of volts they mark %N1 or %N2 and call it a tach guage. Fan or turbine speed respectively.