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David/Sabremech,
The comment “I briefly worked on one in Lancaster Texas and wrote the inspection program for it before it was sold” really interests me. Can you tell me which aircraft it was that you worked on and if you kept a copy of the inspection program that you wrote? Was that 70AL when it was owned by Chevron? I’d also be interested to hear about any additional details, experiences, or information that you might be able to share about it.
As far as the other comment is concerned, “The PT-6 powered Goose is called a McKinnon Turbo Goose. Last count there were 2 I knew of with PT-6's and maybe one with Garrett 331's on it.” - there are only two “real” McKinnon-built model G-21G’s still flying: N77AQ (s/n 1205; ex-Grumman s/n B-62) and N70AL (s/n 1226; ex-Grumman s/n B-125.)
N640 is registered as a "McKinnon" G-21G but it has a data tag that says it is a G-21C - it is not really either of those! It was Grumman G-21A s/n B-123 and it was modified with turbine engines and other McKinnon mods (STC’s) in 1967, but it remained a "Grumman" model G-21A certified under TC 654, albeit with the notation that it was a “hybrid” or a “turboprop” - at least as far as McKinnon himself was concerned, up until and even long after his death in 1991. It was bought surplus from the Alaska Dept. of Public Safety by Larry Teufel of Portland, OR in 1996. Larry subsequently filed paperwork that Grumman G-21A s/n B-123 was “disassembled and scrapped” in 2001.
Shortly thereafter (still in 2001 - almost 10 years after McKinnon died) Teufel claimed to have "built" his own “McKinnon” G-21G out of "spare" parts. He even filed a FAR 47.33(d) affidavit that his “amateur-built” airplane “conformed to an approved type design”, but instead of listing himself as the builder as he should have, he listed “McKinnon” as the builder and registered the aircraft as a “McKinnon” G-21G. He also used an invalid serial number and data tag - in my professional opinion that is and here's why:
The “real” McKinnon serial number 1201 was a G-21C with four Lycoming GSO-480 engines and it ceased to exist as such in 1960 when it was converted by the McKinnon factory into a model G-21D – still with four Lycoming GSO-480 engines. That aircraft, N150M (ex-Grumman JRF-6B s/n 1147), was later converted a third time when the four Lycoming piston engines were removed and two 550 shp PT6A-20 turbines were installed sometime around 1965-1966.
The data tag that is in N640 now says that it is a McKinnon G-21C, serial 1201, and that it was modified under STC SA1320WE in 1968. That never happened as the archived records for N150M and N640 in Oklahoma City still show. To be consistent with all of the other paperwork, N640 should be registered (with a corresponding data tag) as an amateur-built “Larry Teufel” G-21G with a serial number such as “LT-01” or whatever. Or he can rescind his claim that B-123 was "scrapped" and he can claim instead to have "repaired" a Grumman G-21A "hybrid" turboprop Goose and "modified" it into a model G-21G configuration (except that there are no and never have been any STCs approved to do that) but that still doesn't make it an actual “McKinnon” G-21G because it was not "built" or ever re-certified as such actually by McKinnon. Nonetheless, it does look and fly like a McKinnon G-21G.
N221AG is also now registered as a McKinnon G-21G, s/n 1240, except that it was not built by McKinnon either. It was created entirely by the Fish & Wildlife Service in Anchorage, AK in the early 1970’s. FWS did have technical support from McKinnon, including engineering support from McKinnon’s engineering firm, Strato Engineering Co. of Burbank, CA, but FWS did all of the work themselves. It is the Goose that has the Garrett TPE331 turbine engines – their installation was based on the Volpar Inc. turbine Beech 18 conversions.
N221AG (N780 at the time) was envisioned by the guys at FWS as the prototype for a new "McKinnon" model G-21F, but the decision was made that it would be a one-off conversion only. As such, they didn’t want to go to the nth-degree to satisfy the FAA in terms of full type certification. As a result, it was supposed to be converted first to the basic McKinnon G-21G configuration per TC 4A24 Section IV (which can only be done by the TC holder - McKinnon then and now Antilles) and then, only after it conformed to the G-21G design, the additional mods (the TPE331 engines and the 40-inch extended cockpit, and the hydraulic gear and flaps) were supposed to have been installed via separate one-time only STC’s. That also never happened.
They (FWS) simply converted it directly to their planned final "G-21F" configuration and glossed over all of the paperwork in between. Based on the official "Airworthiness" documents (i.e. Forms 337 etc.) filed with the FAA and stored in the archives in OK City, they seemed to have started calling it a McKinnon G-21G one day in March 1974 - there is NO documentation of any kind that accounts for the supposed conversion to a G-21G configuration. There is also no evidence that McKinnon ever worked on the aircraft directly - therefore it is not a "McKinnon" product at all and cannot be properly identified as such under TC 4A24.
There is one other turbine Goose still in existence: N642 is in Oshkosh and it is owned by Jack Mark’s company, MA Inc. Jack died two years or so ago. N642 is registered as a McKinnon G-21C (serial no. 1204) but even though that was accomplished by McKinnon himself, it is also not valid. Just like N221AG and FWS, McKinnon claimed to have simultaneously converted the aircraft under TC 4A24 to G-21C configuration and installed the STC’s to achieve the turbine engines installation. The FAA apparently told him that he was wrong to do it that way, but they never did anything about it.
There were actually two McKinnon STC’s to install the PT6A’s on G-21 airframes, but one was approved only for use on Grumman G-21A’s and the other only for McKinnon G-21C’s or G-21D’s. The resulting airplanes have vastly different gross weight certifications, so it literally makes a big difference which way it is done. The reason is that the turbine engines have nothing to do with the weight differences; there are separate structural reinforcements necessary for the increased weights.
N642 does not have all of the requisite structural modifications specified in the McKinnon model G-21C Master Drawing List No. 7 and it also has never had the four Lycoming GSO-480-B2D6 supercharged piston engines installed; therefore it is not and never has been a "real" G-21C. It should still be registered, as was N640 prior to Teufel’s ownership, as a Grumman G-21A “hybrid” or “turboprop” and it also should have retained its original Grumman serial (B-137).
There were still other McKinnon turbine conversions of Gooses:
N150M (s/n 1251) was already a G-21D (as mentioned above) when it was converted to PT6A-20’s in 1966. It had an extended nose with four additional passenger seats up there. It was rumored to have been seized and scrapped in Haiti or Cuba in the 1990’s.
N660PA (s/n 1203) crashed at sea near Dutch Harbor in the Aleutians in 1996. It was also registered as a G-21G, but that is suspect as well. It was converted from Grumman JRF-5 s/n B-138 (N501M) by McKinnon in 1968, and just like N642 it was re-registered as a model G-21C; it became CF-BCI in Canada immediately after the conversion was finished. Also just like N642, it was not really a McKinnon “C” model either; it was really still just a Grumman G-21A “hybrid” (i.e. turbine) conversion. Each of them might have qualified as a G-21E except for the fact that the model G-21E was not approved under TC 4A24 until a year later in July 1969.
In 1984, Lindair Services in Richmond, BC, put the more powerful PT6A-27 engines on C-FBCI and started calling it a McKinnon G-21G. However, it takes a lot more than just the bigger engines to conform to the G-21G configuration per McKinnon Master Drawing List MPD-90995 and normally aircraft "modified" in the field do not get re-designated as a new model; they technically become just modified examples of whatever model they were originally certified as. Pen Air of Alaska bought it and put it back onto the US civil registry in 1991 or so. They operated it in commercial service until it was lost in a crash in 1996. The real "kicker" in that case was the mods done by Lind Air to make it into a "G-21G" really just made it finally conform to its nominal identification as a model G-21C modified with turbines per STC SA1320WE.
N121H was the one and only official McKinnon model G-21E. It was originally Grumman G-21A s/n 1013 and it was bought by the Halliburton Company in 1954 or so. In 1969-1970, they had McKinnon convert it to the G-21E turbine configuration; it was issued McKinnon serial no. 1211 and re-registered as such. Halliburton sold it in 1991 and after changing hands a couple of times, it ended up with Stallion Air in Chicago. It crashed during some touch-and-go’s in the pattern at DuPage in June 1995.
C-FAWH (Grumman s/n 1083) was never officially issued a McKinnon serial number – although some Web sites say it was. I’ve seen claims of both “1201” and “1202” but those were each completely different aircraft. It was converted to turbines by means of a McKinnon STC kit by Marshalls of Cambridge in the UK, while it was registered there as G-ASXG and it was later incorrectly re-registered in the UK as a "McKinnon G-21C" but still with its original Grumman serial number - 1083 (That is just wrong however you look at it!) So many people still assume that a G-21C is a turbine and therefore if a Goose is a turbine, it must be a McKinnon G-21C. They need to try and actually read the TC! After going to Canada and being re-registered as C-FAWH (eventually as "Grumman G-21A s/n 1083" once again) and it was eventually returned to its original R-985 radial engine configuration in 1986. Even so, it retained its McKinnon windshield and “radar” nose. It crashed at Port Hardy, BC in 1988 and the wreck is still located in a junk yard near the end of the runway there.
So, that was probably more than you ever wanted to know about McKinnon Gooses. If you are able to help me out with that inspection information, it would be greatly appreciated. Thanks for the interest and hopefully some help too.
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