Leagal Mininmums with HGS question.

[andysim 0]

I was watching the SAS Video from AERO presentations and the captain said the HGS allows a lower legal minimums when hand flying but I would love to know what this diffrence is. Anyone know? PS Ive done 1 very low vis ILS with the HGS and its fantastic to see the runway overlay before the runway itself =)

[Ralgh 43]

The HUD allows the pilot to had fly down to CAT III minimums where non HUD planes must do auto lands on CAT III. That is down to 50 feet. the non HUD planes can only be hand flown down to the normal ILS minimums of 200 feet. American Airlines 737s actually cannot do autolands. The company has determined it is way cheaper and easier to keep the planes certified for CAT III HUD landings than autolands.

[andysim 0]

cool thanks! gonna try that later hehe.

[3-2-1-Now 126]

The reason is because with the HUD you are not only looking where you are going, but you have an instrument presentation showing current aircraft parameters. The FPV is the biggest aspect in this, as it shows the current aircraft trajectory, overlaid on the "view out the window", simultaneously. Where the pipper is pointing, the aircraft will land (or crash), and directly increases the accuracy of "putting the aircraft where you want it". If you tried to fly the FPV on the PFD, and then looked out the window, you don't actually know where the aircraft will end up with any useable degree of accuracy, hence the requirements for higher minima on instruments, and thus more time is spent flying the latter part of the approach by visual references only, and as a consequence, it requires higher minima. I found an instant improvement in my visual approaches with the HGS. It has been a long time coming to commercial aviation. Best regards,Robin.