445 

Federal Aviation Administration, DOT 

Pt. 25, App. I 

that sense engine failure, transmit signals, 
actuate fuel controls or power levers or in-
crease engine power by other means on oper-
ating engines to achieve scheduled thrust or 
power increases, and furnish cockpit infor-
mation on system operation. 

(b) 

Critical Time Interval. 

When conducting 

an ATTCS takeoff, the critical time interval 
is between V

1

minus 1 second and a point on 

the minimum performance, all-engine flight 
path where, assuming a simultaneous occur-
rence of an engine and ATTCS failure, the 
resulting minimum flight path thereafter 
intersects the Part 25 required actual flight 
path at no less than 400 feet above the take-
off surface. This time interval is shown in 
the following illustration: 

I25.3

Performance and System Reliability Re-

quirements. 

The applicant must comply with the per-

formance and ATTCS reliability require-
ments as follows: 

(a) An ATTCS failure or a combination of 

failures in the ATTCS during the critical 
time interval: 

(1) Shall not prevent the insertion of the 

maximum approved takeoff 

thrust or power, or 

must be shown to be an improbable event. 

(2) Shall not result in a significant loss or 

reduction in thrust or power, or must be 
shown to be an extremely improbable event. 

(b) The concurrent existence of an ATTCS 

failure and an engine failure during the crit-
ical time interval must be shown to be ex-
tremely improbable. 

(c) All applicable performance require-

ments of Part 25 must be met with an engine 
failure occurring at the most critical point 

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