Originally Posted by Jet II
Who do you work for - in over 20 years in the industry I have never known any major airline insist on fitting ground lock pins for pushback.
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There was a time from about 1979-86 ish when it was a required procedure on the Tristar. There was a failure mode of the undercarriage selector mechanism which retracted the gear with hyds on and an AC power failure. In all that time we used NLG lock pins for push back. We had special ones made with long metal sticks on them so they could be easily removed after pushback. Since then I have never used them on pushback. The hydraulics are pressurised and the pin is redundant. It would need the failure of two big springs, and the hydraulics, and the tug to give a push.
When towing aircraft unpowered, we use a NLG pin only. Some airlines here use all the gear pins, but our airline does not require it, and I agree with this. NLG usually retracts forwards, which means the tyres roll across the tarmac. MLG retracts sideways so the tyres have to scrub across the tarmac.