Generally reliable and reputable news sources such as the Arizona Daily Sun, Arizona Highways, and Phoenix New Times have articles that reference the concrete slab as a helipad. (The Daily Sun article even quotes Jane Jackson, a relief fire lookout who also called the slab a helipad). But news sources get things wrong all the time. So that's not conclusive.Everyone likes to think that's a helipad, but it's just the foundation of the former lookout tower.
The history of fire lookouts on Kendrick seems a bit murky, but there's been something up there since the cabin below the summit was built in 1911 and is listed on the National Historic Register. There are countless photos of this building online.
The current tower was apparently erected in 1964. There are also countless photos of it and it is still in use today.
There was a previous lookout on the site built in the 1930s according to the National Historic Lookout Register. It states that the old lookout was an L-4 structure (a 14x14 wood-frame structure that could be mounted on the ground or on a tower). If the current slab was the foundation for this 1930s lookout, it should be 14 x 14 feet. It doesn't appear that the current slab is square so that doesn't seem to be the case. If the L-4 tower was mounted on a tower, there would be tower footings rather than a slab. I can't find any historic photos of this tower published online.
This site quotes news clippings that indicate a lookout was built in 1914. I can't find any additional reference to this tower.
Now to the slab itself. It appears to have 5 sides. I haven't measured, but looking at photographs you can add up the 16" CMUs that line the slab to determine the dimensions to be 16 feet on the three square sides. You can also see that the slab has received some crack filler / maintenance over the years. So it appears that it is being maintained for some purpose rather than allowed to deteriorate. I'm not an expert on ageing concrete, but neither the slab nor the CMUs give me the initial impression of something that has weathered the top of a mountain for over 60 years.
This photo also seems to indicate that the slab was poured in 1979 based on an inscription in the concrete which reads
*Note Kaibab Helitack was established in 1976.
The Kendrick Peak Lookout tower does not have road access and it was built before the Kendrick Peak Wilderness was established in 1984 by Congress. Wilderness designation prohibits the landing or operation of helicopters within the wilderness. Exemptions can be made, but are rare. After a discussion with the lookout on my trip to the summit a few weeks ago I learned that the tower is not supplied by helicopter, but rather by hiking and pack animals. I was unable to find any photos online of a helicopter on the landing pad on Kendrick, nor any published Forest Order that exempts helicopters from wilderness regulations in the Kendrick Peak Wilderness.
So what does this all mean? I'm not sure!
My guess, based on the research I've outlined above, is that while there was at least one previous lookout structure on the summit of Kendrick Peak prior to the one that stands today, the concrete slab that visitors frequently rest on is actually a helipad, and was constructed in 1979. It's entirely possible that it has not been used as a helipad since Wilderness designation in 1984 (with the likely exception of the Pumpkin Fire or SAR operations that can get emergency exemptions to wilderness flight restrictions). It is certainly possible that the helipad was constructed on the site of a previous lookout structure that once existed there, but I can't find any photos or information about the previous structures.
I don't have enough officially sourced data to conclude that the slab is or is not a helipad or old foundation. If anybody has any additional information that contributes to this, please post a reply! I find this kind of thing fascinating.