Originally Posted by
atpcliff
I know of two pilots taxiing a 747-400, that were stopped short of the mark by the marsheller. They were pissed, because they both looked out the Capt's window and could clearly see there was nothing in their way. They couldn't understand why the marshaller stopped them early. After they got out of the aircraft, they decided to check their obstacle clearance, to show the marshaller he was wrong. When then got to the wingtip area, they could see they would have hit the object. The Capt was very experienced. Both Capt and FO were 100% sure they were safely clear of the object. In the -400, it is VERY difficult to tell how much room you have, and the 747-8 is worse.
There are ways to ensure you are aware of whether you have sufficient clearance such as for each wingtip and outside edge of main gear that require advance preparation.
While at a gate waiting for your freight delay one day, have a crew member, who has been properly briefed for this procedure, go out and stand at several locations, so that can you to take some pictures of him.
For example, the first location, which was briefed, is to stand in front of the aircraft so you can easily see him out your window but with him ensuring that he is always aligned with the left wingtip. Make sure your seat is adjusted so you are at the designed eye reference point(using the three reference balls).
Signal him to move forward or aft as required(with him always ensuring that he stays aligned with the wingtip).
When he reaches the location where your view of him is such that his image touches the aft edge of the main window, get him to stop and stay in position. He is now the obstacle that you can see would just barely strike the wingtip if he was tall enough.
Note his location for the memory banks(how far up from the base of the window). One can also put a camera where your eyes were located and take a picture.
The same can be done for the other wingtip and for gear or even outboard engines. Note: a gear leg position will be an intersection with the MCP panel.
One might forget these reference points when an obstacle situation arises, so you could print off the pictures you took and have them in your notes(if you carry such stuff) for the rare occasion where you are in a tight situation. Then you could stop, set the park brake, get your pictures out, ensure your seat adjustment places your eyes at the reference point and know if you would clear that object.
It may sound odd to take the time to do this but my company provided these pictures to us during our training, which I carried with me. Otherwise, you are just guessing if you will clear an obstacle. And we have had more than one wing tip strike....which is probably why they started providing pictures to us.