The 45 degree entry was recommended to give you a better view of the pattern. Not everyone uses a radio. An army green L-2 can be pretty difficult, if not impossible, to see when it is slightly lower. A straight in approach, while not illegal, is not recommended in the AIM for situations such as this.
I guess the 45 degree entry makes sense from that standpoint, but to me, it seems it can degrade your view of traffic at that critical moment- when you are turning or about to turn downwind. It's very likely that traffic on the departure-end half of the downwind will be in your blind spot. They will likely see you, but with the potential distractions of preparing to land, they might not see you in time. Entering crosswind, or even extended downwind, you will have more trouble spotting traffic in the approach half of the pattern, but unless you are a lot faster than them, this shouldn't be an issue. They will constantly be moving ahead of you. Meanwhile you will get a good look at the critical half of the pattern, especially if you fly a close xwind leg near the departure threshold (which also helps keep you out of the way of departures). You will see departures well, and all downwind or entering-downwind traffic will be within 90 degrees of your nose. Entering on a 45, there is a point where this is not so. To me, this is the key weakness of this kind of entry. Radios or no, there is a serious danger zone as traffic converges at 45 degrees, as opposed to 90.
Another thing: I assume the rectangular pattern we know developed to avoid traffic converging on one line (final)... the pattern forces everybody (flying similar types) into trail, at the same altitude, which adds a safety buffer. Very smart. Works great.
But in a way, that 45-degree-to-midfield-downwind entry, which most PP students are conditioned to fly as if it were law, can create the same problem as not having a pattern: pilots are out there trying to fly to more or less the same point so they can enter the pattern. Fundamentally this is no different than "every man for himself to final". Granted, it could happen on extended crosswind or extended anything, but to me, having more options than "45 to downwind" makes the pattern safer. If everyone slavishly uses "the 45" it can make trouble.
When I was a noob, I was so keen on "the 45" that I'd often take pride in doing all sorts of descending turns, etc so I could fly right over the field (to exercise precise navigation) then drop into what seemed the best spot to "hit the 45". It took me a while to see the danger in this, for me and others. It began to sink in the first time I found myself in a turn a few miles out, trying to roll out on a specific heading at TPA, while trying to find two other pilots whose radio calls indicated they were more or less where I was, because they were also trying to execute this entry! And they didn't see me, even though I was banking! Ulp! Nobody knew quite where to look, that was the key problem. Why create this stress and this hazard? If I enter on the crosswind, any nearby traffic should be at TPA, in a fairly predictable location (because they will be in the pattern). Again, flying a close-in xwind leg keeps you from running over someone climbing on the "normal" crosswind after takeoff. As I cross the centerline on my xwind, I might see him, I might not, but I will most likely be turning downwind before he does, and unitl then we should be flying parallel, not converging.
Extended downwind: also pretty safe. If someone is crosswind, even climbing after takeoff, they will be easy to see, moving across my field of vision. Ironically, the most hazardous traffic when you are downwind is the guy entering at 45 degrees!
He's less likely to really be at the correct angle, and could be joining the downwind leg almost anywhere. Also more likely to get closest to you when he is in your blind spot. It's not a bad way, pre se, to enter the pattern, but it isn't the best, IMHO.
But I definitely see your point regarding low straight-in traffic on final. It's not just camo'd planes that are hard to spot amongst ground clutter, that's for sure.
I think a straight-in should not be an excuse to start descending on final farther out that you normally would, any more than an excuse to dive in from above TPA near that same point. And of course you should be lined up well before that one-mile (typical) point, not hitting the centerline as you start to descend at the normal point. But it could be argued that most straight-in approaches get a little low, and often don't line up with the runway until they are quite close. However, this is not an inherent flaw in flying straight in, it's about how it's executed. I think it would be best, if your course heading would make a straight-in really desirable, to line up before you finish descending from cruise (if possible), call it in early and often, and don't descend thru TPA until you are a mile (or so) from the threshold.
If a straight-in flyer does this, and descends at the same point that pattern-flyers are turning base-to-final, it should be as easy to see them as a plane at any point in the pattern, right? I mean, at that point, they may as well be turning from base. Maybe he's NORDO, and you don't see him until he descends, but so what? If you are past midfield on downwind and don't see a plane at the base-to-final point before you turn base, you need glasses (or a new scrip). If you are on base, OK, he's on final, you should be able to keep a safe distance, or maybe you gotta go around.
I've never been forced to go around or by a straight-in approach, now that I think about it. Haven't seen too many, or executed many, but I've had issues with other people's too-long downwinds, sloppy base legs, etc. and I sure have flown my share of sloppy patterns. But I've never had a problem flying a straight-in or accomodating one.
I also definitely agree about radios- to me, they are a luxury in this situation. Nice to have, but not necessary, and no substitute for good scanning (and thinking).
Anyways... I'm rambling, I know. I am just fascinated by how much stock is put in "the 45", even though it's just another way to do it, really only as safe as the pilots involved, and has weak points that other entries do not have.
