Contaminated surfaces significantly complicate control by increasing the actual Vmcg.
How so ? Vmcg is based on nil nosewheel steering input and the numbers consider friction characteristics.. it may be prudent to consider a reduction in crosswind limits for tyre force considerations .. However, a low speed go decision can provide an interesting piloting experience.
JT,
You got me doubting my fading (only a tiny bit) memory, so I dusted off the C-5 performance manual which is where I remembered Vmcg being corrected for contamination as well as crosswind. Calculating Vmcg was done as part of each take-off, run by the F/E and checked by the captain. Now, it’s on calculators, then paper spaghetti charts.
I ran a few samples and my memory was correct, there were corrections for each. With Zero crosswind, 0C, these are my results for three conditions: dry Vmcg (69 KIAS) to wet Vmcg (87 KIAS) to compacted snow (97 KIAS). Yes, the chart is titled Vmcg, 3-engine, no nosewheel steering. I can only guess the reason is that while on the ground the forces opposing the yaw are applied thru the tires. I’ve never looked elsewhere or seen Vmcg charts on civil types.
BTW, the beast increased Vmcg for crosswind component almost exactly 1kt for 1kt.