View Full Version : S76 Undercarriage Failure to extend. Indications, combinations of safe & unsafe light
slizer58
22nd Mar 2014, 07:14
If you are recovering back to base and the undercarriage is not able to extend after following all EOP actions as well as failure of ground staff to manually pull the gears down.
a) Would you utilize the emergency blowdown or
b) Deploy the floatation gear.
+ presuming all Hydraulics AOK
212man
22nd Mar 2014, 07:34
If you haven't already blown the gear down how can you say you've followed all the EOP actions?
Fareastdriver
22nd Mar 2014, 08:20
My personal experience is that you blow the gear down. If you want to remain friends with your airport operator blow it down over the grass. It saves them having to clean the sprays of hydraulic oil off the concrete.
Mast Bumper
22nd Mar 2014, 16:12
I've had to blow the gear down manually once. The story about oil spraying everywhere is a myth, nothing of the sort happens.
However, because we didn't trust the gear even after blowing it, the pilot in the right seat got out of the helicopter while the pilot in the left seat (PF) kept the helicopter light on the wheels. The rights seat pilot proceeded to pin the gear before we lowered the collective all the way and taxied to parking to offload the passengers.
ShyTorque
22nd Mar 2014, 16:36
If normal hydraulic system pressure couldn't lower the gear, why should a less powerful, gas powered emergency system?
The blowdown system is designed to be used when there is no No. 2 hydraulic pressure or no DC Essential Power.
As per the emergency checklist.
If normal hydraulic system pressure couldn't lower the gear, why should a
less powerful, gas powered emergency system?
Can the utility system priority valve fail in such a way that stage 2 hydraulic pressure is normal, but utility system pressure is below what is required to operate the gear?
The Tox
23rd Mar 2014, 00:06
Yes it can, and had it happen. The subsequent investigation revealed that when the pilot selected gear down,the landing gear hyd system pressurised down, the gear extended normally but on landing, hyd system fluid was seen flowing down from the front of the flight control deck and over both the windscreens. The deck was awash with 5606. Further investigation revealed a very tight hairline crack in the underside of a pressure pipe that opened up when pressure was applied, the spray from the crack was very fine and not of sufficient flow rate to trip the priority valve until the reservoir was emptied.
Fareastdriver
23rd Mar 2014, 10:18
Mast Bumper:
The story about oil spraying everywhere is a myth,
I was there. I did it. Have you?
I had a No2 hydraulic failure 90 miles offshore in IFR. At my destination I had to go around at 200ft owing to 100ft/150m. I then flew to my alternate another 70 miles away; all this on one hydraulic pump.
On arrival I blew the gear down in the hover before landing over a brand new apron. Believe me, there was a fairly widespead oil stain and a very pi@@ed off airfield operator.
This was in the early eighties where hydraulic pumps were lifed 'on condition'. The one that had failed had 1850 hrs on it.
The one my life depended on had 2100.