The 737 NG Performance Improvement Package (PIP) was a series of aerodynamic and engine improvements including refined wing control surfaces, redesigned wheel-well fairing, a streamlined anti-collision lights, ECS inlet/exhaust modulation and the new CFM56-7BE "Evolution" engine (see powerplant). The total fuel saving with PIP is 2%.
The PIP was introduced as standard into production 737 NGs in stages from line number 3570 in March 2011 to line number 4302 in December 2012. Some of these improvements have also been made available for retrofit to earlier NGs.
Details of the individual improvements are given below:
*** Updated 23 Nov 2020 ***
The CFM56-7BE “Evolution” package was delivered from L/N 3700 July 2011 with the following improvements:
The 7BE engine can be identified by the exhaust configuration. The nozzle is 18” shorter and exhaust plug is 2.5” shorter, although it looks longer because of the much shorter nozzle. The heat shield above the nozzle has new titanium pans, inboard plume suppressors and side scoops to cope with the higher temperatures from the new short exhaust configuration.
The -7BE gives a 1% fuel saving and an improved EGT margin over the -7B with no noise ro emmissions penalty. Also, Engine maintenance costs are reduced up to 4% for the highest thrust
rating; the higher the thrust rating, the greater the maintenance cost
The only slight disadvantage was a revised (slightly reduced) in-flight starting envelope and a revised procedure with a more formal definition of a warm vs. cold engine. Boeing took the decision to adopt the new restricted in-flight start envelope as the common standard across the NG fleet for simplicity and to allow engine intermixes.
CFM56-7B Exhaust nozzle/plug
CFM56-7BE Exhaust nozzle/plug
The -7BE will be able to be intermixed with regular SAC/DAC or Tech Insertion engines subject to updated FMC, MEDB and EEC.
New low drag anti-collision lights
From L/N 3570 (March 2011) onwards, the upper and lower anti-collision lights were changed from a cylindrical to an oval shape to reduce drag. The upper skin was revised to reduce the risk of crack migration. This upper skin revision eliminated the weight reduction milling of the doubler in the area under the light but, because of the structural change, no retrofit has been offered.
New low drag wheel well fairings
From L/N 3570 (March 2011) onwards, the aft halt of the main wheel well farings (the half that face forward into the airflow) have been reshaped from a rectangular to a curved form to reduce drag.
Spoiler and slat trailing edge modifications
From L/N 3570 (March 2011) onwards, there were the following three modifications:
1. A reduction in the spoiler trailing edge thickness on spoiler 1, spoilers 3 through 10, and spoiler 12.
This change will reduce drag
2. A reduction in the gap between the spoiler trailing edge and the flaps
This change reduces drag by reducing the gap between the spoilers and the flaps. These gaps were initially set to a higher nominal position to improve the lateral control handling qualities on the 737-700. With various lateral control system changes, the increased gap sizes are no longer needed and have therefore been reduced.
3. A reduction in the thickness of the slat trailing edge.
change will reduce drag by reducing the thickness of the trailing edge wedge.
The new spoilers and slats are fully interchangeable and intermixable with the previous spoilers and slats. Retrofit is at customer discretion.
ECS ram air inlet and exhaust modifications
From L/N 4302 and on (December 2012) The existing ram air inlet actuators were replaced by new "smart actuators" which give position feedback and communicate with the added ram air exit actuators. The inlet actuator is mounted at a slightly different orientation than the current actuator, requiring changes to the airplane structure to accommodate, so retrofit is not available.
The ram air exit was changed from a plain oval shaped duct opening to a rectangular duct with three exit louvers. The exit louvers are actuated by a series of shafts and linkages that are driven by the added exit actuators that are the same part numbers as is being used on the new inlet actuators. To accommodate installation there are structural changes forward of the wheel wells on both sides of the aircraft.
The system (inlet and exit) is tuned to open and close together at a very specific relationship to optimize thrust recovery of the air exiting the exhaust louvers, thus reducing fuel burn of the aircraft.