Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Aircraft
Startup and taxi out was normal. Takeoff roll was normal; but slight vibration developed at about 60 KTS. I moved slightly off center to avoid runway lights; which slightly improved the noise and vibration. Then it got worse; just as First Officer called 100 KTS. I considered high speed reject and decided it was safer to continue. I had excellent centerline control and no indication the airplane could not fly. Vibration decreased slightly as weight shifted aft and I gently rotated. Rotation was normal; and control was fine except for loud noise and vibration from nose wheel shimmy. I was surprised that shimmy noise did not immediately dissipate after rotation and airborne and delayed retracting the gear momentarily. All flight controls were functioning normally. Retracted gear and the noise and vibration stopped. We had a normal climbout. Checked status pages and maintenance history; all seemed fine. Once safely at altitude; we discussed our options. Climbout and cruise were normal; and there was no safety advantage to landing heavier than planned. Our destination had 12;000 [feet of dry runway] and clear weather so there was no safety consideration of finding a longer or better runway. That was when the comm issues started. We sent several messages to Dispatch asking them to call us. Tried text messages and an ACARS Call Me request. We also communicated with Maintenance Control about a lost and found issue; and they answered that one. We had sent a maintenance message. I again texted Dispatch to call me with Maintenance Control on the line regarding the nose wheel problem. No luck.Finally they ACARS'd to call them on a VHF frequency. which I did but got no answer. I tried every VHF frequency in the Flight Operations Manual COMM page for non-U.S. operations; including all the commercial and foreign FSS and foreign radio operators. Nothing. Maintenance Control sent an ACARS message to try different HF frequencies. We had to inform them that we did not have HF radios. Tried ATC for suggestions and they gave us HF frequencies. It was while we were over the Midwest that I tried reaching Maintenance Control. Finally; over foreign airspace; I gave up and tried 121.5. A commercial flight with SATCOM and HF relayed for us; but I never did get Maintenance or Dispatch input. We advised ATC we wanted emergency equipment to standby for landing.After considering the issues; and terrain; it seemed like it would be a good idea to keep the gear down in case of a missed approach. Also; we wanted to stop on the runway and assess. Therefore; having decided to deviate from SOP; we declared an emergency and advised we did not need assistance until landing. We made a normal landing to a full stop and requested an inspection. Maintenance then came and towed us to the gate. Mechanic plugged in and deliberately lied to me; claiming things were normal but he would tow us in. Later explained he didn't want to scare us because the damage to the nose wheel was so bad. FAA personnel met us at the jetway door with pictures showing much of the right nose wheel was gone. They had already alerted the company.
A B757 flight crew experience significant landing gear vibration during the takeoff and requested emergency equipment standing by on landing. One nose gear tire was found to be substantially missing. Communications problems with the company enroute were a significant contributing factor to the flight's uneasiness.