First officer reported that after starting APU at the gate to cool aircraft; ground personnel report...

Attributes
ACN	1669112
Time
Date	201907
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Parked
Flight Plan	IFR
Person 1
Function	First Officer
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Procedural Published Material / Policy

Narrative:

Sitting at the gate loading [passengers] we turned on the APU to cool the cabin. After turning on the bleed air the ground crew alerted us that the engines where starting. The crew looked at the engine instruments and the only indication of a start was N1 at 1.5 % or so. The crew also noticed both start switches in ground. The start levers where in cut off. The crew had no intention of starting the engines and where shocked to see the start switches in ground. All earlier checklist had been completed and the crew did not know how the start switches where moved to ground. The crew immediately put the switches in off. It was less than two minutes the switches would have been in ground. Make sure all checklists are completed. Also I will be doing a double check the start switches are in off before opening the app bleed valve.

Original NASA ASRS Text

Title: First Officer Reported that after starting APU at the gate to cool aircraft; ground personnel report both engines starting; requiring Flight Crew to turn off APU Bleed Air and investigate; discovering both engine start switched were left in Ground Position.

Narrative: Sitting at the gate loading [passengers] we turned on the APU to cool the cabin. After turning on the bleed air the ground crew alerted us that the engines where starting. The crew looked at the engine instruments and the only indication of a start was N1 at 1.5 % or so. The crew also noticed both start switches in ground. The start levers where in cut off. The crew had no intention of starting the engines and where shocked to see the start switches in ground. All earlier checklist had been completed and the crew did not know how the start switches where moved to ground. The crew immediately put the switches in off. It was less than two minutes the switches would have been in ground. Make sure all checklists are completed. Also I will be doing a double check the start switches are in off before opening the app bleed valve.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

First officer reported that after starting APU at the gate to cool aircraft; ground personnel report both engines starting; requiring flight crew to turn off APU bleed air and investigate; discovering both engine start switched were left in ground position.