Date: 201411
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Air Conditioning Distribution Ducting; Clamps; Connectors
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Physiological - Other; Confusion; Communication Breakdown; Situational Awareness
Second reporter function: Captain
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury; Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: Other During Maintenance
Result: General Maintenance Action
Contributing factors: Procedure; Human Factors; Aircraft; Staffing
Primary problem: Human Factors

Narrative: Report is due to Flight and Cabin Crew operating flight XXX to ZZZ; deadhead to ZZZ1; overnight and operating flight following morning back to ZZZ. Flight Crew reported to Maintenance a squeal in the cabin during Deadhead to ZZZ1. Line Maintenance arrived to investigate and requested Flight Crew to start engines with [Main Cabin] door shut. After listening in the cabin at normal pressure levels on the ground; Maintenance put aircraft pressurization system into manual mode and descended the cabin until reaching 3.0 psi and back to unpressurized; approximately 15 minutes. Crew experienced uncomfortable ear pressure but no other medical concerns. Maintenance tightened a connection in Pack-1 and Aircraft returned to service. In ZZZ; the following morning; Captain obtained a copy of the Maintenance procedures including the BOLD WARNING about non-essential personnel not being onboard. This pressurization took the flight crew to a cabin altitude below sea level; there is concern similar to a scuba dive. Pressurization and flight at altitude may not have been advisable. Company Medical was called; but by this time it was 24 hours past the pressurization event. The flight attendant; who has a hearing impairment and wears hearing aids; reported being more plugged up than usual and was removed at Company Medical Doctor's request. The Flight Crew unaware pressurization to 3.0 psi was planned. Line Maintenance did not have copy of procedure with them. Flight Crew unaware of potential hazard due to no briefing from Maintenance personnel and no written copy of maintenance procedure. Ensure that when procedures are communicated from Maintenance Control to Line Maintenance; that warnings are transmitted. Provide written guidance on Flight Crew assisting Maintenance or provide adequate personnel to perform procedure without ANY assistance from Flight Crew.

Callback: Reporter stated the air conditioning packs on the EMB-145 are located in the wing root area under the cabin seats. The cabin pressure controller knob is extremely sensitive and controlling a rate of descent of 500 feet per minute is very difficult in the manual mode. The EICAS display indicated the cabin pressure had gone down to 1;500 feet during the ground pressurization leak check. What the actual pressure ended up being; he is not sure; but flying at altitude after that may not have been advisable as he learned later.

Second narrative: Crew was Deadheading in the cabin on an EMB-145 aircraft to ZZZ1 and heard a squeal sound when pilots added power. Upon landing captain informed Maintenance Control. Control contacted ZZZ1 contract mechanic to investigate a squeal sound in the aircraft cabin. Maintenance Control directed crew to start engines while contract mechanic and Maintenance Control investigated the squeal. Contract mechanic was on the phone with Maintenance Control. The mechanics believed the issue was a loose connection in the PACK systems. However; without the flight crew knowing; Maintenance Control directed contract mechanic to conduct an 'air check.'Crew was unaware of this procedure and not briefed prior. Contract mechanic did not have a checklist. Flight Attendant was onboard. Contract mechanic; under the direction of Maintenance Control; and without warning to the crew onboard; pressurized the cabin substantially below sea level using the manual mode pressurization system to achieve a 3.0 psi pressure differential. Crew and contract mechanic experienced uncomfortable ear pressures during the procedure and the procedure was stopped within 15 minutes. Contract mechanic tightened the PACK connections and under the direction of Maintenance Control the contract mechanic signed off his work. Crew did not report any medical conditions preventing the safe operation of the aircraft. Flight operated safely back to base; conducting flight back to ZZZ. This report is being submitted for the operation of two flights; ZZZ-ZZZ1-ZZZ; because the crew were on board an aircraft which was pressurized below sea level prior to these flights. The concern arises from the possibility that pressurizing the aircraft to a pressure below sea level may expose flight crews to injuries similar to those of scuba divers. Captain contacted Maintenance Controller X who stated that this procedure was not dangerous. Captain obtained the 'leak check' procedure from ZZZ Company Maintenance department and found the procedure was not what the crew witnessed. The crew did not have prior knowledge of the Medical Warning found on page one of the procedure. Captain contacted ZZZ Chief Pilot who did not know how to proceed but directed the captain to Company Medical. Captain called Company Medical whose Doctor concluded that further flights would be safe because 12-hours had elapsed from the exposure. However; Flight Attendant; who wears hearing aids was removed by Company Medical Doctor to evaluate ear conditions prior flying again.Crew was not briefed that Maintenance Control had directed contract mechanic to conduct a 'leak check.' Contract mechanic under the authority of Maintenance Control conducted the check without a visual checklist. This is not the first report captain has submitted highlighting the prevalence of Maintenance Control talking contract mechanics through a procedure via telephone. This practice is potentially dangerous especially if the WARNINGS in the procedures are not communicated to those persons inside an aircraft during these procedures. Company should issue written standards to the flight department outlining the approved procedures which would allow pilots and crew to assist contract mechanics with the servicing and maintaining of the aircraft fleet. These verbal procedures are potentially hazardous especially to flight crew because flight crew often operate in extreme environments and with limited time on the ground to acclimate or recover from exposures. Because the FAA relies largely on the science of the Center for Disease Control (CDC) for infection control procedures; then FAA should likely consult hyperbaric medical societies for procedures involving aircraft pressurization and the standards for medical screening of crew and passengers involved in these procedures and involved in inflight rapid depressurization events.


Synopsis: A Contract Mechanic was directed by Maintenance Control to pressurize the cabin of an EMB-145 aircraft to below sea level in the manual mode. Flight crew and Flight Attendant were not made aware after being requested to start engines with the main cabin door closed. Uncomfortable ear pressure was experienced. Crew departed in the morning; but pressurization and flight at altitude may not have been advisable due to scuba dive effect.