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The definition of the acrobatic category in FAR 23.3 reads as follows:

(c) The acrobatic category is limited to airplanes that have a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for use without restrictions, other than those shown to be necessary as a result of required flight tests.

Considering that the Northrop T-38 is a two-seat, twin-engined supersonic jet trainer aircraft with a USAF service maximum takeoff weight of 12,093 lbs (from their factsheet), what traits of the T-38 would have prohibited Northrop from applying for a civil Type Certificate for the T-38 in the acrobatic category?

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  • $\begingroup$ What is a civil type certificate. $\endgroup$
    – Ethan
    Commented Sep 23, 2015 at 22:46
  • $\begingroup$ @Ethan It is basically a certificate issued by the regulatory authorities signifying the airworthiness of an aircraft design. i.e. it signifies that the particular aircraft design is safe to operate subject to conditions in the certificate. $\endgroup$
    – aeroalias
    Commented Sep 23, 2015 at 23:37
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    $\begingroup$ A type certificate - civil or otherwise - costs a lot of money to obtain. Once obtained there are costs associated with maintaining it. If the potential market is not big enough to sustain these costs, there is no business case to seek the certification. $\endgroup$
    – Monolo
    Commented Sep 24, 2015 at 10:40

2 Answers 2

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That an aircraft is eligible for a category is not a basis to say that the aircraft should be certified in that category. In other words, though there is nothing prohibiting T-38 being certified in acrobatics category, FAA will not certify it unless someone approaches it for that reason.

The T-38 would come under military surplus aircraft, which is covered by FAA Advisory Circular 20-169 for Military and Special Mission Modifications and Equipment for Commercial Derivative Aircraft.

However, there are some T-38s being operated by civilians in US, which are type certified under FAA Experimental Category (most are used by NASA, Boeing etc for research). One of the aircraft owned by Thornton Corp. is certified under the 'Exhibition' category, which permits the user,

to exhibit an aircraft’s flight capabilities, performance, or unusual characteristics for air shows, motion pictures, television, and similar productions, and for the maintenance of exhibition flight proficiency.

I'm not sure if this aircraft has been used in that manner though.

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  • $\begingroup$ F-5 (Fighter version of the T-38) were used as stand in for russian MiG's in the Top Gun movie, I don't now if that counts. $\endgroup$
    – Essah
    Commented Sep 24, 2015 at 14:02
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    $\begingroup$ @Essah, those F-5s were (maybe still are) used for Dissimilar Air Combat Training, but they were operated by the US Navy, not by a civilian operator thus not requiring a Type Certificate. $\endgroup$
    – Marco Sanfilippo
    Commented Sep 24, 2015 at 14:27
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The short answer is the FAA has recently moved to a flight test basis for certification of civilian aerobatic aircraft.

The average human body can withstand (https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2091-61.pdf) +4-5G's before loosing consciousness. To be certified for acrobatic maneuvers The FAA had previously required an aircraft be certified for at least +6 and -3g.

However, according to https://www.faa.gov/regulations_policies/rulemaking/recently_published/media/Part23_FinalRule_2120-AK65_WebCopy.pdf, "For the reasons explained in the NPRM, the FAA removed the acrobatic category from part 23. The FAA agrees with Velica that the limitations for an airplane certified for aerobatics should be based on flight tests, but believes more specificity is warranted. Therefore, the FAA will require airplanes certified for aerobatics to comply with the limitations established under subpart G of part 23 in this rule."

As already stated, military planes do not have to comply with Federal Law but the Govt does attempt to comply when reasonable (or cost effective) to do so. Interestingly, a YouTube Video (I was unable to find the link) documenting the Airforce F16 Thunderbird's said the F16 engines had to be extensively modified for aerobatic show performance. In other words, military aircraft are normally designed for only a few seconds of inverted flight.

So the FAA is now using a flight test basis for certification of civilian aerobatic aircraft.

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  • $\begingroup$ "The average human body can withstand +4-5G's before loosing consciousness." That figure can be dramatically increased with proper physical conditioning, awareness, and anti-GLOC techniques. $\endgroup$
    – Michael Hall
    Commented Feb 27, 2019 at 0:12
  • $\begingroup$ But only for a few seconds. $\endgroup$
    – jwzumwalt
    Commented Feb 27, 2019 at 5:42
  • $\begingroup$ Depends on your definition of a few. Have you been through military centrifuge training? $\endgroup$
    – Michael Hall
    Commented Feb 27, 2019 at 6:40
  • $\begingroup$ According to this military training study, <a href=google.com/…> most military pilots began gray out at 5g@5s or 4g@10sec to be "g" rated they must do 9g@10sec and 40% washed out! $\endgroup$
    – jwzumwalt
    Commented Feb 27, 2019 at 7:10
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    $\begingroup$ I can't dispute the results of their study, but I am a retired military pilot and I have been through centrifuge training. With some basic training on G awareness and training on techniques to mitigate the effects a pretty average pilot is fully capable of sustaining 4-5 Gs for far, far longer than that. A little bit of tunnel vision or "grey out" is not at all the same thing as losing consciousness. $\endgroup$
    – Michael Hall
    Commented Feb 27, 2019 at 17:09

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