So, if I had a plane flying about 5000 feet overhead, what visual clues could I use to tell if it was an EMB-135 or a CRJ-100? From what I can tell they are generally the same shape with similiar engine mounts, but I wans’t sure if anyone knew some good clues.
keme.co.uk/~supanova/colinsp … 22_089.jpg
petitmonde.com/MaFamille/Uti … ageId=2749
The first one is a ERJ 135 and the second is a CRJ100 I think that the body on the CRJ100 is wider then the ERJ135 but i’m not to sure. I tried to get the underside because its what you saw. it also looks like the ERJ 135 the nose it more pointed. But like i said i’m not to sure. 
When you can only see one at a time, there are two good hints:
The CRJ-100 has winglets, while the ERJ-135 doesn’t.
The CRJ-100 has a two piece engine covering, while the ERJ-135 has one piece.
If you can see both at the same time, or you’ve seen a lot of both, the CRJ is shorter and fatter (4 across) while the ERJ is longer and skinnier (3 across).
I’m not sure what you mean by a one-piece engine cowl on the ERJ-135. I maintain six ERJ’s. The bottom cowl is hinged on one side and latched on the other. It swings open and has a ‘kickstand’ to keep it open. The top half of the cowling must be lifted straight up. It’s a bit tricky. There are two places for hooks to attatch and lift it off the engine. So I think it could be considered a two-piece cowl.
You’re getting too technical for simple spotting. The ERJ’s have one simple engine cowl, which is continuous, and the CRJ’s have an engine cowl, which ends and has a metal engine cone sticking out the end.
Gotcha…I misunderstood. Thanks for clearing that up. Good day.