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Maintenance
N4521R · Cessna 172N · As of Oct 20, 2026
Annual inspection
ScheduledDue Nov 30, 2026
Last Nov 20, 2025; due by the end of the 12th calendar month after.
14 CFR 91.409(a)
ELT inspection
ScheduledDue Nov 30, 2026
Last Nov 20, 2025; due within 12 calendar months.
14 CFR 91.207(d)
ELT battery
ScheduledDue Jun 20, 2028
The replacement date marked on the transmitter (also due after more than 1 cumulative hour of use).
14 CFR 91.207(c)
Transponder check
ScheduledDue Nov 30, 2026
Last Nov 20, 2024; due within 24 calendar months.
14 CFR 91.413
Altimeter and static system
ScheduledDue Nov 30, 2026
Last Nov 20, 2024; needed for IFR, within 24 calendar months.
14 CFR 91.411
VOR check
UpcomingDue Nov 07, 2026
Last Oct 8, 2026; needed for IFR using VOR, within 30 days.
14 CFR 91.171
Latest compression
Sep 12, 2026
Engine
663.4 h to TBO
1,336.6 hours since overhaul of a 2,000-hour TBO.
At your 73.4 hours a year, the 2,000-hour TBO comes in about 9 years (Nov 3, 2035). This counts hours only: a calendar limit or the engine's condition isn't included.
Notes
No notes yet. Saved notes are listed here, newest first.
Engine trends
Your readings, compared over time.
Show the numbers
| Date | Iron | Copper | Aluminum | Lead (from avgas) |
|---|---|---|---|---|
| Apr 3, 2025 | 14.7 | 4.6 | 5.1 | 3,907 |
| Jul 30, 2025 | 15.5 | 4.5 | 5 | 3,429 |
| Oct 30, 2025 | 15.7 | 5.5 | 6.9 | 3,348 |
| Apr 25, 2026 | 15.9 | 4.5 | 6.4 | 3,639 |
| Sep 6, 2026 | 18.7 | 5.2 | 5.9 | 3,854 |
40 entries · View readings
Compression history
Each check compared with the one before.
| Checked | Cyl 1 | Cyl 2 | Cyl 3 | Cyl 4 | Note | |
|---|---|---|---|---|---|---|
| Sep 12, 2026 | 74.5/80 (-0.5) | 75/80 | 67.5/80 (-1.5) | 75.5/80 (-0.5) | — | |
| Feb 12, 2026 | 75/80 (-0.5) | 75/80 | 69/80 (-1.5) | 76/80 (-0.5) | — | |
| Sep 26, 2025 | 75.5/80 (-0.5) | 75/80 | 70.5/80 (-1.5) | 76.5/80 (-0.5) | — | |
| Feb 2, 2025 | 76/80 | 75/80 | 72/80 | 77/80 | — |
Latest readings (Sep 12, 2026, psi)
Oil analysis (ppm)
| Sample | Hours on oil | Iron | Copper | Aluminum | Chromium | Nickel | Silicon | Lead | |
|---|---|---|---|---|---|---|---|---|---|
| Sep 6, 2026 | 26.9 | 18.7 (+2.8) | 5.2 (+0.7) | 5.9 (-0.5) | 1.2 (-0.2) | 2.2 (+0.2) | 6.5 (+0.2) | 3854 (+215) | |
| Apr 25, 2026 | 27.8 | 15.9 (+0.2) | 4.5 (-1) | 6.4 (-0.5) | 1.4 (+0.2) | 2 | 6.3 (-1.8) | 3639 (+291) | |
| Oct 30, 2025 | 25.1 | 15.7 (+0.2) | 5.5 (+1) | 6.9 (+1.9) | 1.2 (-0.1) | 2 (+0.2) | 8.1 (-0.3) | 3348 (-81) | |
| Jul 30, 2025 | 27.9 | 15.5 (+0.8) | 4.5 (-0.1) | 5 (-0.1) | 1.3 (+0.1) | 1.8 (-0.2) | 8.4 (+2.1) | 3429 (-478) | |
| Apr 3, 2025 | 26.2 | 14.7 | 4.6 | 5.1 | 1.2 | 2 | 6.3 | 3907 |
Oil additions
The date and how much you added. Oil burn is worked out from the hours in your logbook in N4521R between additions.
12.9 hours per quart on average: 142 logbook hours over 11 quarts added.
- Apr 3, 2025: 13.3 hours per quart (13.3 hours, 1 quart).
- May 30, 2025: 12.9 hours per quart (12.9 hours, 1 quart).
- Jul 9, 2025: 12.8 hours per quart (12.8 hours, 1 quart).
- Aug 22, 2025: 12.6 hours per quart (12.6 hours, 1 quart).
- Oct 8, 2025: 12 hours per quart (12 hours, 1 quart).
- Nov 26, 2025: 13.3 hours per quart (13.3 hours, 1 quart).
- Mar 8, 2026: 13.4 hours per quart (13.4 hours, 1 quart).
- Apr 25, 2026: 12.8 hours per quart (12.8 hours, 1 quart).
- Jun 7, 2026: 13.3 hours per quart (13.3 hours, 1 quart).
- Aug 27, 2026: 12.4 hours per quart (12.4 hours, 1 quart).
- Oct 12, 2026: 13.2 hours per quart (13.2 hours, 1 quart).
| Date | Quarts added | Logbook hours since the last | Hours per quart | |
|---|---|---|---|---|
| Oct 12, 2026 | 1 | 13.2 | 13.2 | |
| Aug 27, 2026 | 1 | 12.4 | 12.4 | |
| Jun 7, 2026 | 1 | 13.3 | 13.3 | |
| Apr 25, 2026 | 1 | 12.8 | 12.8 | |
| Mar 8, 2026 | 1 | 13.4 | 13.4 | |
| Nov 26, 2025 | 1 | 13.3 | 13.3 | |
| Oct 8, 2025 | 1 | 12 | 12 | |
| Aug 22, 2025 | 1 | 12.6 | 12.6 | |
| Jul 9, 2025 | 1 | 12.8 | 12.8 | |
| May 30, 2025 | 1 | 12.9 | 12.9 | |
| Apr 3, 2025 | 1 | 13.3 | 13.3 | |
| Nov 28, 2024 | 1 | — | — |
Log compression
Each cylinder's gauge reading, then the number it's out of (80 unless your gauge set says otherwise).
Your mechanic interprets changes in these readings.
Add an oil analysis
Read the lab's report, or type the figures in. You check them before they're saved.
Or type the figures in
Log oil added
The date and the quarts you added.
Add a reminder
Anything you want a heads-up on by a date: it shows with the inspections, in Needs attention 30 days ahead, and in the weekly email.
Reminders use the dates you enter and your logbook, under 14 CFR 91.207, 91.171, 91.409, 91.411 and 91.413. They are not a maintenance record.