Operation Manual Part 2

Aerosoft – Digital Aviation

CRJ-70 & CRJ-900

AOM PART 2

Systems Description

VOL

5-1-118

26-Jul-2017

FLEX POWER

The logic behind the flex thrust concept is simple. Air gets thinner with rising temperature – you probably

noticed that aircraft need more runway on a hot summer day than in winter (given the same weight of course).

By entering a ‘flex temperature’ – it is called “assumed temperature” - the computer is made to believe that

you are flying on a hot summer day instead of the, colder, persisting conditions. This means the maximum N1

setting will be lowered, and so reducing wear on the engines (and slightly reducing noise as well).

The flex temperature needs to be calculated for each take-off and each configuration of aircraft weight,

runway and environmental conditions like temperature, air density, head wind component and so on. This is

normally done by a flight performance tool or looked up in huge tables. Some operators run own departments

only being in charge to track their aircraft’s fleet performance and keep flight planning tools, performance

calculators in sync with their fleet’s performance figures. This is also the explanation why we are not able to

provide any performance tables regarding flex temperatures. But always remember that use a flex

temperature means you have less thrust available.

In case you want to use a flex temp with the CRJ you need to enter the flex temperature on the PERF MENU

page of the FMS. You can also set it via the EICAS menu.

Flex temp may only be entered when the following conditions persist:

• Thrust levers are in idle or shutoff

• Aircraft is on ground

• The temperature entered is higher than the ambient temperature.

• Airspeed is less than 65 knots

AUTOMATIC POWER RESERVE (APR)

The automatic power reserve is a feature which enhances the power of the remaining engine in case an engine

fails. It is available during take-off and go-around only.

APR is armed during take-off when N

reaches take-off thrust within 8% of the commanded setting. On

approach, APR is armed for go-around with either engine available, flaps greater than 20° or landing gear

down.