RBC capital’s Mike Abramsky was the first analyst out of the gate Friday with a note to clients assessing the effect on Apple (AAPL) of the explosion at Foxconn’s Chengdu plant.

According to Abramsky, the plant is one of two primary manufacturing sites where the iPad 2 is produced, the other being Foxconn’s original Shenzhen facility. His sources disagree, however, about the two plants’ relative importance. Some believe the majority of iPads were being manufactured at Chengdu; others say that Chengdu was having trouble ramping up, and that the majority of iPads were still being manufactured in Shenzhen.

Accordingly, he offers two scenarios: (I quote)

1) Serious Business Impact. Under this scenario, Chengdu manufactures most iPads and the explosion is serious; i.e. Apple is unable to utilize alternatives or get back on stream by June. If so, it could be negative for Apple’s Q3 (June); stoppage of Chengdu until end June may equate to the lost production of 1.8-2.8M units Q3, which is 22-36% of our expectations for 8M iPad shipments Q3. If Foxconn is unable to pick up the slack by June, it could also cause production shortages for Q4/F11 (end Sept). Under this scenario, Q3 revenue may be impacted by $1.1-1.7B (4-7%) and EPS $0.35-0.55 (6-9%), which at current valuation represents $5-7 downside to shares.

2) Less Serious Business Impact. Under this scenario, either Shenzhen still makes most iPads and is unaffected, and/or Foxconn is able to re-start iPad production quickly at Chengdu. Estimating a 1 month production impact, would perhaps equate to <1.3M units Q3 with limited impact to Q4. Under this scenario, revenue would be impacted by <$800M (<3%) and EPS <$0.26 (<4%) which at current valuation represents less than $3 downside to shares.

The fact that Apple’s shares dropped only 1% on Friday suggests to Abramsky that investors are pricing in scenario 1. (Apple fell another 0.5% to close the day at $335.22.)

For videos of the aftermath, see here.