Questions regarding block-protection and helper units

Helpers on the head end(front)required a stop to uncouple and move them to a side track/spur track,
helpers on the rear end(back) could be cutoff "on the fly" on freight trains by the conductor in the caboose
by closing off the angle cock(valve) on the brake pipe and pulling the coupler pin to release the helper as it slows down
at the release location.
Helpers on passenger trains are required to stop to take off the helpers.

mcnoch wrote:

Backshophoss wrote:helpers on the rear end(back) could be cutoff "on the fly" on freight trains by the conductor in the caboose
by closing off the angle cock(valve) on the brake pipe and pulling the coupler pin to release the helper as it slows down
at the release location.
Helpers on passenger trains are required to stop to take off the helpers.

Thanks. Two follow-up questions to your answers.
Do all freight trains still have a caboose at the end of the train or only those were helps have to be released? The photos in my books normally show only the front section with the leading locomotives.
If a helper unit is released will it continue to trail the train until they can move to a side track or can they move directly into the opposite direction to get back to the station?

The only regular use of Cabooses in current North American railroad service nowadays is as "Shoving Platforms" to protect trains which must do long backup moves across multiple grade crossings. In these cases a crew member (usually the conductor) rides on the back platform of the caboose and can use the brake valve to slow or stop the train. AFAIK,there is no usage of cabooses in helper service at all anymore.
Manned helpers are much less common now; especially on the major Class 1 railroads due to widespread use of "Distributed Power Unit" technology. This involves locomotives cut in to the middle and/or end of a train and remotely controlled by radio signal from the lead engine. Where manned helpers are still used in situations where that are cut off "on the fly", my understanding is that the rear end locomotives do not have their air hoses connected to the train they are pushing so the brake valve issue is moot..

Now the conductor or brakeman on the pushers can open or close angle cocks, and pull pins.

It is legal to not couple hoses. The alternative is to dial in the marker's code. This way the helper engineer to know if the head end is applying the brakes. If the train goes into emergency the helper knows to shut off.

I heard that Conrail had devices to remotely pull pins on helpers. I fuelled they might have also controlled the helpers air automatically based on the info from the marker. I'm sure someone who works in Altona will answer.

Modern helpers on NS' Allegheny Mountain crossing (Horseshoe Curve) use "Helperlink". This ties the helper locomotives into the EOT system via the radio signals from the lead locomotive. It also allows the helper Engineer to pull the pin without leaving his seat. BNSF also uses this system on Crawford Hill in Nebraska, and Ranchester Hill in Wyoming. See Al Krug's "Krug Tales" explanation of the system along with a photograph here;

http://krugtales.50megs.com/rrpictale/h ... erlink.htm" onclick="window.open(this.href);return false;

When I was in management training 30+ years ago, I was sent to a location where helpers were routinely used to get out of town. Helpers went ahead of the caboose (still in use then). Once over the top, the helpers and caboose would be cut off on the fly and then the caboose cut off from the helpers (IIRC, air was cut in to the helpers and caboose so cutting them off also involved closing angle cocks while in motion - what can I say, it was a different time). At the controlled siding just after the summit, once the train was clear, the operator would line the helpers into the siding, then once they were in, line it back, give the caboose permission past the stop signal, and they would drop by gravity until the caught up with the train and couple up on the fly. When they finally reached some place where they had to stop, they'd' finally reconnect the air to the caboose.

For the record: The OP's orignal post (mcnoch)and that person's 1st reply are missing from this thread,
a possible victum of the recent spam attacks to this site.