Date: 201902
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Cockpit Window
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Procedure; Incorrect / Not Installed / Unavailable Part; Human Factors; Manuals
Primary problem: Human Factors

Narrative: While climbing out of ZZZ we observed a pressure squeal from First Officer R2 sliding window at 9000 feet MSL. I have observed pressure leaks on prior flights but this one was exceptionally loud and rather alarming. Climbing out of 10;000 feet we conducted the Climb Checklist where we verified that the aircraft was pressurizing properly. The leak was clearly coming from my R2 window and I ensured that the window was secure/closed and could not feel any air rushing around the window. The Captain and I decided to continue climbing as pressurization; outflow valve; and control panels all were normal in hope that the leak would close as was common with leaks observed in past flights. However; in this case; as we obtained clearance to FL230; it was clear that this leak was not closing and was extremely loud and even painful to our hearing. We discussed the problem; and faced with an extended over water flight duration planned at FL410; we determined the risk was too high to continue flight and the Captain directed that we divert to ZZZ1.As with any unplanned diversion and dealing with the physiological distraction/unpleasant noise; task saturation was a consideration and the noise an additive crew factor. We began [dividing] up tasks to decrease workload and the Captain handled flying and talking with cabin while I worked with ATC and handled FMC programming and Dispatch communication. I informed ATC of the need to stop climbing and divert to ZZZ1. We did not not declare an emergency. Center issued new clearance to ZZZ1 including an arrival transition and I set up the automation for arrival into ZZZ1 while the Captain informed the flight attendants and passengers of the situation. Aircraft landing weight was not a consideration; which allowed a prompt landing into ZZZ1. We completed the diversion plan and other checklists/briefings and received proper authorization form Dispatch via ACARS. During final approach we observed the pressure leak finally cease at 5000 feet MSL. Maintenance met the aircraft when we arrived at ZZZ1.A quick assessment by Maintenance determined that the window seal drain hose had become stuck in the window after closure. Upon further inspection the mechanic determined that the drain hose was not an FAA approved part and had no part number. The hose was very flexible and appeared to have no rigidity. He explained that this should be a dark grey rigid hose that is not bendable. Instead; this hose had a very flimsy structure and resembled a surgical rubber hose of some type. Clearly; it was not able to properly fit in the designated area near the window which allowed it to interfere with side window operation. Operations made arrangements for an aircraft swap and we deplaned the passengers and cargo. Flight was completed on a new aircraft approximately 1:40 minutes behind original schedule.I would suggest measures be taken to ensure window seal drain hoses are of approved composition/installation and do not interfere with window operation.


Second narrative: Flight from ZZZ. On climb out passing 9000 feet; the R2 window/First Officer side sliding window started whistling and during the climb out continued to get worse. The pressure was checked normal and was normal the entire flight. The whistling became painful to the ears and unbearable passing 18;000 feet. In the flight levels at FL230 the crew decided to divert to ZZZ1. The plane continued and landed at ZZZ1 with an uneventful flight divert and landing. The painful whistle noise stopped as we were descending through 5000 feet.ZZZ1 Maintenance discovered the part causing the seal whistle was the Right Side Window Sill Condensation Tube. This tube appeared to be the wrong part as the tube installed was what appeared to be a flimsy piece of loose surgical tube; as compared to the Window Sill Condensation Tube on the L2 Captain's side; which was rigid and correct. In addition; the airplane we changed to in ZZZ1 with our plane swap had the correct tube on the R2 window and no tube installed on the L2 window. The Window Sill Condensation Tubes within the fleet may all need to be checked or understood as to what is the minimum requirement and the correct usable safe part.


Synopsis: B737-700 flight crew reported diverting due to a cockpit window air leak.