I don't understand the logic of the FR marker and the T-shaped head of the amber low speed caution range on the speed tape during takeoff, particularly at high gross weights.If I perform a takeoff at a gross weight of 280.00mt with flaps 25 Temp 14C (no flex), the following happens...The aircraft climbs initially at about 190 KIAS as per the target speed. This is sitting right on the green FR marker. My understanding is that once your speed exceeds this marker and it turns green, it is safe to retract the flaps! After passing ACCEL altitude, the magenta circle moves to VCL and the aircraft accel past FR speed. The FR flag turns green - however, if you go ahead and retract the flaps, the T-head of the low speed buffet tape moves a good 10KIAS above the green FR flag, bringing the the current airspeed very close to the low-speed buffet. Sometimes, if the autopilot isn't flying the speed EXACTLY on target, the pitch mode will enter Low Speed Protection mode. Surely this shouldn't happen? Surely the head of the low speed caution range should always come up to meet the FR flag when the flaps are retracted, never above it? As is the case when the slats are retracted, the yellow tape doesn't go above the SR flag.Also...Why does the head of the low speed caution range move up when ACCEL altitude is passed and the commanded speed increases to VCL? At high gross weights this also brings the aircraft too close to the low speed protection range with only a couple of knots to play with!Thanks in advance!Martin Neep

There was a big debate about this over a year ago and the concensus was that the FR marker does not indicate the maximum flaps extended speed like a Boeing would, it indicates the minimum possible speed to retract. Tip your nose level at FR speed and you wont need speed protection

FR marker does not indicate the maximum flaps extended speed like a Boeing would, it indicates the minimum possible speed to retract.

Is that not what I said?Martin Neep

Is that not what I said?Martin Neep

Sorry, I should have said "Minimum possible speed in straight and level flight".

Minimum possible speed in straight and level flight

Where did you read this? There's no reference to it any of the manuals:

FR Bug (Flap Retract, source: FM) - The FR bug is normally green and appears only when the flaps are extended. The FR bug will be removed when flaps are retracted. The FR bug turns amber if:-Current airspeed is below FR speed or-Flaps are extended at FR speed + 10 Knots or-Flap display below speed tape is amber for any reason

So according to the above, the -FR flag should remain amber until the aircraft has exceeded this speed by 10 knots and not turn amber as soon as it is passed?Martin Neep

Where did you read this? There's no reference to it any of the manuals:

You wrote it. http://forums1.avsim.net/index.php?showtop...t&p=1532123

I didn't write anything about the aircraft having to be "straight and level"Martin Neep