Hi,Some discussion about this elsewhere. Couldn't find it in any of my manuals, so help (Ian maybe?) needed. What is that white box on the nose gear assembly ??Terohttp://www.ee.oulu.fi/~partanen/nose.jpg

Nose Gear Steering Actuator System.There is a small switch on the top that a by-pass pin goes into, that allows for the aircraft steering to be disconnected from the hydraulics, an lets a tug push the aircraft back on the ground.The Pin is atttatched to a large Flag that the ground crew hold up to show the crew when the tug and towbar is disconnected. This tells them the Nose Gear Steering system is reengaged.

Indide the box is something called the summing mechinism, that centers the steering after the steering tiller is released (there are rig pin holes in here also when the nose wheel steering is initially rigged), the box also protects some of the phenolic steering pulleys and cables.

"What is that white box on the nose gear assembly ??"I'll let you know just as soon as I've figured it out myself, Tero :-lol There are a few hundred pages on this in my manuals.http://members.ozemail.com.au/~b744er/767/UnderTheCover.gifLooks like some very non-Avionic type bits to me ;-)Cheers.Ian.

Ian,While you are thinking about that mystery, please confirm what HPSOV once said, that the rad alt sensors are located ~ 5m behind nose gear on a 757/767.Also, what is the exact location of the RA sensors on a 747-400 ?Tero

If I remember correctly, the RA sensors on the 757 are about half way from nose gear to main gear.George DorkofikisAthens, Greece

"...please confirm what HPSOV once said, that the rad alt sensors are located ~ 5m behind nose gear on a 757/767."I had the exact location in terms of station numbers somewhere, but can't seem to find those values at the moment, Tero. In their absence, here's a pic...http://members.ozemail.com.au/~b744er/767/RadAltAntennae.jpgDifficult to spot in the pic, but the sequence of bits and pieces on the lower forward fuselage is (from the nose gear back), Main Equipment Centre hatch, Lower TCAS antenna(usu. circular, shallow dome shaped), Lower ATC Antenna (small red blade type ), Equipment Cooling exhaust (big black hole with air rushing out of it.... Watch your toupe!)... VHF Comm antenna (Left? system, large, blade-type, with red/white stripes), DME Antenna (Left system, small red blade type), then the Rad Alt (six small flat grey rectangular plates), followed by another DME Antenna (Right system, small red blade type), Marker Antenna (not visible) and finally, another VHF antenna. Location may vary with some antennae.The 767 has 3 Rad Alt systems (for redundancy). Each system has two antennae: one transmit antenna (forward one), one receive antenna (aft one).Most aircraft have the Rad Alt Antenna in roughly the same spot, although you may find some weird ones, like the 747SP (antenna behind the main gear). Their location determines (to a great extent) what readout will be present on the cockpit instruments with the airplane parked at the gate. Minus values if forward of the main gear, plus values if aft of the main gear.If you need precise values, it may take me a little longer to come up with them (I don't think my tape measure is long enough ;-)).Cheers.Ian.

Ian,Excellent information once again!I'll pass about the numbers (although it would be nice to know, but it's gonna mean too much work for you with the tape and all :D).Do you remember, if 747-400 has the antennas at roughly same spots ?Tero

"Do you remember, if 747-400 has the antennas at roughly same spots ?"A bit off topic, Tero, but... I'll save you a trip to the PS1 forum ;-)Using Station numbers... where Station 90 = tip of nose... and each station unit = 1 inch.Transmit Antennae = Station 893 (i.e. 893 minus 90 = 803 inches from the tip of the nose). Receive Antennae = Station 933 (i.e. 933 minus 90 = 843 inches from the tip of the nose).For info, the bulkhead at the rear of the nose wheel well is about Station 400.Hope this makes sense.Cheers.Ian.P.S. Here's a diagram I prepared earlier for showing people why Rad Alt heights are negative when the nose comes down (values applicable to the 747-400 only)...http://members.ozemail.com.au/~b744er/RadAlt2.gif

For a minute there I forgot what site I was on and entered some details for the 737, but here are the numbers for the 767... :-)767 Rad Alt Transmit Antennae = Station 577767 Rad Alt Receive Antennae = Station 621.The Centre System Antenna are right on the airplane centerline, the L and R system antennae are 14.1 " outboard of this.The tip of the nose is Station 92.5.Calculations of distances from the main gear can be complicated because of the weird station numbering system on the 767-300.... You have to add extra length because of the insertion of longer fuselage sections (compared to the 767-200).Hope this helps.Cheers.Ian.