Originally Posted by
Xeptu
There was or is a time limited prohibition range which applied to the smaller F70 engine. Unfortunately the software is the same for both the F70 and F100. The issue is that should this condition be tripped it cannot be cleared by the pilot and cannot continue on until it is, along with any maintenance conditions applied of course in the case of the smaller F70 engine.
Today most dinosaurs have the same problem, there are few if any software engineers who still hold the approvals and skills to make changes to fundamental operational software. Even if there is, since the manufacturer no longer exists who carries responsibility for those changes. It’s not all that simple both software packages must be changed in order to ensure the right software is applied to the right engine. The easier solution is to implement an operating procedure which is less likely to cause the issue. This in itself creates new problems if it’s not though through and most often comes to light literally by accident.
For example for the F50, it came to light that pilots couldn’t be trained reliably to properly reject a takeoff bringing about a significant increase in stop distance. The solution was to lock out reverse and rely on brakes alone. It follows then that the takeoff antiskid inop charts and procedure must be removed also, it wasn’t. I would be curious today as to how many think they can still takeoff with antiskid inop. It will certainly come to light the first time someone rejects a takeoff with no reverse and no antiskid.
When on the B744 with a Big Airline in UK, Idle Rev was the `SOP on all landings, unless runway conditions were adverse.
Less engine wear, and carbon brakes cheaper than engine life. Plus I suppose a small fuel saving.
This is still the norm on all types from A380, 777/787 to A320 etc.