Shop Talk: Aircraft Clocks

March 16, 2010

Wish you had a better understanding of the regulations when talking to your mechanic or the avionics shop? Aircraft Electronics Association Vice President of Government/Industry Affairs Ric Peri answers your frequently asked questions.


Question: Per FAR 91.205(d)(6), for IFR flight a clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation is required. Does the clock have to be installed in the aircraft, or can the pilot meet the requirements of the regulation by wearing a wristwatch?”

Answer: The clock must be installed in the aircraft, and no, a wristwatch does not meet the regulatory requirement.

The following is, in part, from a 1981 legal interpretation from the FAA to an individual who had asked the agency a similar question. While the question from the letter is focused on the MEL aspect of Part 135, the answer clearly addresses the use of a wristwatch in lieu of an installed clock.

Operator’s question:

“The aircraft is airworthy except the clock installed in the cockpit is inoperable. Would flight be allowed under Section 135.179 if there were no MEL and if the pilot in command possesses a reliable operating watch on his person?”

FAA’s answer:

If the aircraft is type certificated for instrument flight rules, a clock is required by Section 91.33(d) [this has since changed to Section 91.205 (d)]. However, even if the aircraft is not type certificated for instrument operations, other requirements apply.

Section 21.181 provides in pertinent part that an airworthiness certificate is effective so long as the maintenance, preventive maintenance, and inspections are performed in accordance with Parts 43 and 91. Section 91.27(a)(1) provides in pertinent part that no person may operate an aircraft unless it has within it a current airworthiness certificate. Section 91.165 provides in pertinent part that no person may operate a civil aircraft unless it is in an airworthy condition, and that between inspections, defects in the aircraft must be repaired as prescribed in Part 43. Thus, to maintain the validity of the airworthiness certificate without a change to the type certificate, the clock must be operating for all operations, and operations with the clock inoperative would violate Sections 91.165, 135.3, and 135.143(a). A wristwatch would not substitute for the clock.

For those who like to ponder such things as the federal aviation regulations, the following is Section 21.181 (a)(1) of the FARs.

Section 21.181 Duration.

(a) Unless sooner surrendered, suspended, revoked, or a termination date is otherwise established by the Administrator, airworthiness certificates are effective as follows:

(1) Standard airworthiness certificates, special airworthiness certificates - primary category, and airworthiness certificates issued for restricted or limited category aircraft are effective as long as the maintenance, preventive maintenance, and alterations are performed in accordance with Parts 43 and 91 of this chapter and the aircraft are registered in the United States.

In this section you will notice a couple of issues to ponder with regards to the clock. As shown previously a wristwatch does not meet the regulations, but what about a “portable” watch such as a stop watch taped to the panel or affixed to the yoke? Is the installation a “proper alteration” as prescribed in Part 43?