This move is made necessary because the current U.S. Army fleet of 230 OH-58Ds is wearing out. Ten years of war have hit the OH-58Ds hard. Those used in Iraq were in the air 72 hours a month, while those in Afghanistan were airborne 80 hours a month. In peacetime these choppers spend about 24 hours a month in the air. Moreover, combat use puts more stress on the aircraft. Plus there's battle damage, which included twenty destroyed in combat. The current solution is to spend several billion dollars to refurbish and upgrade the current fleet to the OH-58F standard and thus keep the OH-58 in service for another 10-12 years. It is believed that a replacement will be found and built before then, or the OH-58 will go through another round of upgrades. This has worked for other military systems (the Sidewinder air-to-air missile, the B-52 bomber, and C-130 transport) so this is not a particularly daring choice. It just works.
The OH-58D has a top speed of 226 kilometers per hour and a range of 241 kilometers. It has a mast-mounted sight, which carries a powerful FLIR (heat sensing camera) and a laser designator. The OH-58F will move the sensors to the body of the aircraft, right in front of the pilots. The OH-58D is lightly armed and usually only carries four Hellfire (anti-vehicle) or Stinger (anti-aircraft) missiles, or 14 70mm unguided (or guided) rockets. The upgrades don’t change the weapons load, and OH-58D users are still arguing for a new engine. Over the decades, the new equipment and weight has been added, without an increase in engine power. For a scout helicopter, the OH-58 was getting more sluggish as it got older. This was not good, even though the OH-58F is five percent lighter than the OH-58D, which helps a bit.
To help ease the workload on the OH-58Ds, the army is reorganizing its light aviation battalions, by removing some OH-58 helicopters and adding RQ-7 Shadow UAVs. The new battalions have 29 aircraft, eight of them UAVs. All this is the result of years of experience with the RQ-7 and some tests, using UAVs as scouts for helicopter gunships or in cooperation with scout helicopters, rather than the traditional scout helicopter (like the OH-58) operating exclusively. The tests were successful, and the army is updating its tactics as well.
In the last decade scout helicopters have been doing a lot less scouting, having been replaced by MQ-1C, RQ-7, and Raven UAVs. The scout helicopter pilots are relieved at having UAVs take over some of the more dangerous missions. In particular, the scout helicopter pilots are glad to lose the job of going in to "draw enemy fire" (and thus reveal where the enemy is). This sort of thing has gotten a lot of scout helicopter pilots killed. But there are still situations where the superior situational awareness (two pilots with four eyes, four ears, and two noses) of humans is preferable. There are some even more basic considerations. The RQ-7 can stay in the air for up to eight hours per sortie, about three times longer than the OH-58, while the new MQ-1C can do four times better than that.
The army is also equipping some of its AH-64 helicopter gunships with digital communications that enables them to see what the UAVs are seeing. The OH-58s often scout for the AH-64s, finding targets. Now the RQ-7s can do it better, by letting the AH-64 pilots see what the RQ-7 has detected. There are also systems that allow the AH-64 or OH-58 pilots to take control of UAVs. The OH-58F will have both of these capabilities. Meanwhile, it's expected that the army aviation battalions will gain more UAVs and lose helicopters.