Thrust Settings

I am a high schooler researching the Ins-and-Outs of commercial aircraft, and am slightly confused with CLB1 and CLB2. From my understanding these are climb thrust max settings for x designated aircraft. Ive seen these terms used almost every time in takeoff (Considering its used for ideal climb thrust). Can anyone help me understand the usage and ideas surrounding CLB1 and CLB2? Thanks
Nash

Nash,

I can only speak in terms of my aircraft (ERJ-175), but CLB1 and CLB 2 is the maximum climb thrust rating based off a % N1. N1 being the percentage of the low pressure section including the fan at the front of the engine. After we have reached acceleration/flap retraction altitude (typically 1000 ft. above ground) and cleaned up the aircraft, we have the option to choose between CLB 1 and CLB 2. CLB 2 is usually the default in our aircraft and is a slightly reduced performance for engine conservation. If we don’t require additional thrust for our climb, we will leave it at CLB 2. If we want improved performance, we can select CLB 1. The difference might only be a minor percentage increase, but it can noticeably improve climb performance.

Ex:
CLB 1: 89.2% N1
CLB 2: 86.8% N1.

The basic answer is that we usually run the engine at reduced thrust for takeoff and climb to conserve the engine and its components.

Roscoe

2 Likes

Nash,

As Roscoe said reduced thrust climbs are more economical and save on engine wear and tear. In most cases the thrust is selected based on the takeoff weight of the aircraft (which is based on passengers, cargo and fuel + the weight of the aircraft). Most airlines have recommendations for which to use for certain weights which compares performance to efficiency (ie. weight < X use CLM 1, > X to Y use CLM 2, > Y no reduction). Make sense?

Adam

2 Likes