Apollo 11 anomalies and malfunctions register — Mission Report §16, transcribed
The complete anomaly summary of the Mission Report (MSC-00171) §16 — “a discussion of the significant problems or discrepancies noted during the Apollo 11 mission” — transcribed entry-by-entry the way the plan-vs-actual transcribed Table 11-I: 28 anomalies (11 CSM, 14 LM, 3 government-furnished equipment), each with its section number, what happened, the consequence, the cause and resolution, and the wiki concept it touches, cross-checked against the Technical Crew Debriefing (Vol. 2). Read from the raw scan (printed pp. 16-1 – 16-23 plus figures 16-1…16-22; PDF pp. 280–323) via its rough OCR text layer, with garbled passages verified against page renders. Quotation marks are the report’s own words; status is the report’s verdict as of November 1969 — 26 closed, 2 still open.
Scope note: §16 covers the two spacecraft and the government-furnished crew equipment; the launch vehicle is assessed separately (§15) and is not part of this register.
16.1 — Command and service modules (11)
Section titled “16.1 — Command and service modules (11)”Every CSM anomaly maps to Columbia — a useful engineering counterpoint to Collins’ debriefing verdict that his circumlunar ship was “reassuringly dull… it didn’t have any failures.” Most were instrumentation- or redundancy-level; the two anomalies the report left open are both here.
| § | Anomaly | What happened — and its consequence | Cause → resolution | Status |
|---|---|---|---|---|
| 16.1.1 | Service propulsion nitrogen leak | During the LOI burn, GN₂ pressure in the redundant SPS actuation system decayed 2307→1883 psia (normal decay ~50 psia/firing); only the one system affected, “no performance degradation,” and no leak during TEI | Contamination-induced failure of a solenoid control valve (suspect: a contaminated facility manifold at the vendor); Apollo 12+ get integral filters | Closed |
| 16.1.2 | Cryogenic heater failure | One of two heater elements in oxygen tank 2 was inoperative; it had failed during launch-countdown pressurization, but “this information was not made known to proper channels” pre-flight (no spec limits in the test procedure); heaters are redundant, so no flight constraint | Probable intermittent contact on a terminal board in the heater circuit (same board type as 16.1.3); launch-site tests now verify both heaters by amperage | Closed |
| 16.1.3 | Automatic-coil failure in one thruster | The CM RCS system-1 minus-yaw engine gave low, erratic thrust through its automatic coils; it worked normally on the direct coils | Two loose pins in a 1966-built terminal board → intermittent continuity (a known pre-Nov-1967 board defect); base-gasket design change; no pre-1967 boards sit in crew-safety circuits | Closed |
| 16.1.4 | Entry monitor system display segment out | An electroluminescent segment of the EMS velocity counter would not illuminate | Consistent with prior misrouted-logic-wire failures (sharp wire ends puncturing insulation); no generic problem indicated; pre-flight checkout being improved | Closed |
| 16.1.5 | Oxygen flow master alarms | Two master alarms during the initial LM pressurization as O₂ flow decreased from full scale — “the only consequence of the alarms was the nuisance factor” | An open EMI-filter capacitor let relay K1 chatter, re-triggering the 16-second alarm timer; duplicated postflight; no corrective action required | Closed |
| 16.1.6 | Propellant isolation valves closed | SM RCS quad B isolation valves shut from pyro shock at CSM/S-IVB separation (as on Apollo 9) | Tests show the magnetic-latch valves close at lower shock than expected, undamaged; crew-checklist precaution retained, no further action | Closed |
| 16.1.7 | Odor in docking tunnel | A smell “similar to burned wire insulation” at first hatch opening — but no discoloration or overheating found in flight | Crew matched the odor to a docking-hatch ablator sample: removing the hatch’s outer insulation (Apollo 11 onward) runs the ablator hotter and increases outgassing | Closed |
| 16.1.8 | Low oxygen flow reading | The O₂ flow measurement sat at the instrument floor instead of the ~0.3 lb/hr metabolic rate — actual flow was normal; indication biased ~−1.5 lb/hr | Flow-sensor heater-winding resistance had risen 1000→1600 Ω, skewing the bridge reference; element too small to depot and analyze; no design problem indicated | Closed |
| 16.1.9 | Forward heat shield mortar lanyard untied | Found postflight: all but one tie-wrap knot on the mortar umbilical lanyard had untied — wrong knot (a clove hitch, not two half-hitches); worst case could have disconnected the mortar umbilical before firing, losing the heat-shield separation-augmentation parachute and risking heat-shield recontact with the CM (it fired correctly on Apollo 10 and 11) | Installation error, present on spacecraft 110/111 too; step-by-step tying procedure written for SC-112, Apollo 12/13 reworked | Closed |
| 16.1.10 | Glycol temperature control valve | Two cooling-control excursions in lunar orbit (slow valve response, then evaporator outlet down to 31° F on rev 15); behavior normalized about when the crew cycled the AUTO/MANUAL switch | Postflight teardown found a gear-train bearing retainer disengaged and interfering with the worm gear; cause of the retainer failure under investigation | Open |
| 16.1.11 | Service module entry | The jettisoned SM did not skip out of the atmosphere as predicted — the crew saw it pass, thrusters firing, rotating; film shows it disintegrating near the CM during entry | Propellant slosh resonating with the spin axis can flip the SM into an unstable flat spin with retrograde thrust; separation maneuver being reassessed | Open |
16.2 — Lunar module (14)
Section titled “16.2 — Lunar module (14)”| § | Anomaly | What happened — and its consequence | Cause → resolution | Status |
|---|---|---|---|---|
| 16.2.1 | Mission timer stopped | Shortly after landing the Eagle mission timer stopped and would not restart; powered off to cool, it restarted 11 hours later and ran normally (the post-landing surprise already noted in planned-vs-actual) | Most probable: a cracked solder joint in the cordwood-construction electronics, remade on cooling; screening for Apollo 12 units; new welded-IC timers in development | Closed |
| 16.2.2 | High fuel pressure after landing | Simultaneous post-landing venting of descent propellant and supercritical helium froze fuel in the fuel/helium heat exchanger; engine heat soakback then drove trapped-line pressure to an estimated 700–800 psia (gauge pegged at 300) against bellows links that yield above ~650 — the exchanger thawed in ~½ hour and pressure decayed without leakage (post-landing propellant ops under powered descent and landing) | Venting procedure changed for future missions (close the solenoid valve before fuel venting; vent helium later) | Closed |
| 16.2.3 | High CO₂ partial-pressure indication | After ascent, the CO₂ reading went high and erratic and tripped a caution-and-warning alarm; canister swaps had no effect — it was the sensor, not the air | Pre-EVA ECS shutdown let water-separator condensate overflow into the suit loop just upstream of the optical CO₂ sensor (“the Commander had noted water in his suit” — see 16.2.13); vent line relocated for Apollo 13 | Closed |
| 16.2.4 | Steerable antenna acquisition | On revolution 14 (the undocking rev) the steerable S-band antenna kept losing lock — downlink lower than predicted, communications hard to hold before descent | The Operational Data Book’s antenna-coverage diagrams were wrong (they omitted the late-added plume deflectors), so the chosen pointing angles sat in or near vehicle blockage, compounded by lunar-surface multipath; correct blockage/multipath maps and attitude work-arounds for future missions | Closed |
| 16.2.5 | Computer alarms during descent | The 1202/1201 story: five Executive-overflow program alarms during powered descent before low gate; “the performance of the guidance and control functions was not affected” | Meaningless counter interrupts from the rendezvous-radar coupling data units (the radar’s 800-Hz excitation source was frequency- but not phase-locked to the PGNS reference, so the CDUs “slewed” digitally at up to ~12.8 kpps, stealing ~15% of a computer already at ~90% capacity); Luminary 1B zeroes the CDUs when the radar isn’t computer-controlled | Closed |
| 16.2.6 | Slow cabin decompression | Depressurization before the EVA “required longer than had been anticipated” through the bacteria filter (EVA equipment); the crew could not have damaged the hatch by pulling early (78 lb opens flow at 0.25 psid; suited 1/6-g subjects can pull ~102 lb max) | Apollo 12+ delete the bacteria filter, cutting the final decompression from ~5 minutes to under 2 | Closed |
| 16.2.7 | Display segment inoperative | An electroluminescent segment died on the abort guidance system DEDA display (ascent’s backup computer), making 3 and 9 ambiguous on that digit — usable but ambiguous | One similar prior failure (cracked electrode from a faulty epoxy process); no generic problem; full-segment prelaunch test added | Closed |
| 16.2.8 | Voice breakup during EVA | VOX-keyed relay voice from the surface reached the Network broken up — mostly Aldrin’s | Most probable: the Commander’s downlink VOX sensitivity set low (both moonwalkers keyed through it; checklist called for maximum); duplicated on the ground at one notch below max; “not an inherent system design problem” | Closed |
| 16.2.9 | Echo during EVA | Houston heard its own uplink echoed back during the EVA relay | Acoustic coupling from earphone to microphone inside the comm carrier at max volume, re-keying the marginally-set VOX (see 16.2.8) — “inherent in the communication system design”; ground procedure changed (inhibit downlink remoting during uplink; CAPCOM simplex backup) | Closed |
| 16.2.10 | Onboard recorder failure | The LM’s DSEA onboard recorder did not record properly — voice very low under a 400-Hz tone, timing signal stuck — which is why no LM cabin transcript exists and the mission’s voice record is three-legged, not four | Most likely two broken 26-gauge wires in the vehicle harness at the recorder connector (same break seen in LTA-8 thermal/vacuum tests); harness taped and stiffened for Apollo 12–15, sheet-metal cover from 16; the out-of-spec prelaunch readings now have limits | Closed |
| 16.2.11 | Broken circuit breaker knob | After the EVA the crew found the engine-arm breaker knob broken and two other breakers closed (EVA equipment); the breaker still closed for ascent — but could no longer be manually opened | Most probable: impact from the oxygen purge system’s aft edge during EVA preparation (demonstrated in simulations); breaker guards on Apollo 12+ | Closed |
| 16.2.12 | Thrust chamber pressure switch | The quad-2 aft-firing engine’s pressure switch responded slowly all mission, then ignored seven straight minimum-impulse commands in the 18 minutes before TPI — a master alarm and thruster warning flag; the engine itself was fine | Probable particulate contamination slowing gas flow into the switch diaphragm; future crews briefed to recognize it | Closed |
| 16.2.13 | Water in one suit | In lunar orbit after ascent, water entered the Commander’s suit “in spurts (estimated to be 1 tablespoonful) at about 1-minute intervals” via the vent duct (EVA equipment / ascent); selecting the secondary water separator stopped it in 15–20 min | Most probable: leakage through a binding water-separator selector valve (actuation took 12.5 lb against a typical 7–8); allowable force lowered to 10 lb, binding inspections added | Closed |
| 16.2.14 | RCS warning flags | Thrust-chamber warning flags on three engine pairs (with master alarms, the crew believed) during station-keeping before DOI and again just before PDI; cleared by cycling the caution/warning electronics breaker | Insufficient data to confirm; most likely a single-point signal-conditioner buffer-module dropout (one +28 V feed serves ten buffers) that cleared itself — thruster response was normal throughout; no corrective action | Closed |
16.3 — Government-furnished equipment (3)
Section titled “16.3 — Government-furnished equipment (3)”| § | Anomaly | What happened — and its consequence | Cause → resolution | Status |
|---|---|---|---|---|
| 16.3.1 | TV cable retained coiled shape | The television cable kept its stowage coils on the surface and “the loops … represented a potential tripping hazard to the crew” (the cable-underfoot problem in lunar dust operations) | Every change investigated (material, stowage, deployment hardware) bought “only minimal improvement” for a weight penalty — no hardware changes planned | Closed |
| 16.3.2 | RCU-to-PLSS connector mating | ”Considerable difficulty” mating the remote-control-unit connectors to the PLSS during EVA prep — the coupling lock ring spun freely, forcing the crew to grip cable insulation to align it (the famous ~10-min-per-unit delay in planned-vs-actual) | Connector redesigned for future missions: positive-position lock ring with 90° capture, conical-tip pins for easier insertion | Closed |
| 16.3.3 | Sample return containers hard to close | Closing force on the rock boxes “was much higher than expected,” compounded by the unstable MESA table and weak retention (sampling tools) | The flight units were unexercised (training units had worn in below the 32-lb limit) and contractor cleaning had stripped the latch-linkage lubricant, adding up to ~24 lb; lubricant now burnished on (≤25 lb delivered), over-center table locks evaluated for Apollo 13+ | Closed |
Crew cross-checks (debriefing volumes)
Section titled “Crew cross-checks (debriefing volumes)”Where the debriefing text carries the crew’s side of a §16 entry (Vol. 2 is image-only from p. 74, so some accounts are reachable only in the report’s own crew citations, quoted in the tables above):
- 16.2.1 (timer) — Vol. 1 §10: Aldrin noticed it at the T-2 stay/no-stay check — “the mission timer wasn’t working… It was frozen” — stopped reading 903:34:47, a time the crew couldn’t correlate with anything.
- 16.2.6 (decompression) — Vol. 1 §10, Armstrong: “it took a very long time to depressurize the LM through the bacteria filter”; the sequence with PLSSs on the backs “was never completely performed on the ground.”
- 16.3.2 (connector) — Vol. 1 §10: the RCU-to-PLSS junction is “about a 50-pin Bendix connector”; “we had had trouble with that connector for 2 years” — the years-old unfixed problem the wiki already records.
- 16.3.3 (rock boxes) — Vol. 1 §10, Armstrong: “It took just about everything I could do to close the document sample box. I was afraid I might have left the seal in the box.”
- 16.2.5 (alarms) — Vol. 1 §9: cockpit “attention was directed toward clearing the program alarms” during the descent — the distraction cost the wiki’s descent concept already describes.
- 16.1.3 (thruster coil) — Vol. 2 §14, Collins, unprompted: “command module RCS thruster 16, yaw left… functioning improperly using the automatic coils” but fine on the direct coil — flagged in-flight as “a possible systems problem”; the postflight terminal-board finding (loose pins) is the answer to exactly that flag.
- 16.1.7 (odor) — Vol. 1, on first opening the tunnel: “there was a peculiar odor in the tunnel… not exactly the same as burned electrical insulation” — matching the report’s ablator-outgassing conclusion.
- 16.1.11 (service module) — Vol. 2 §14, Aldrin: “It flew by to the right and a little above us… really spinning” — the crew observation the report cites in declaring the SM’s entry behavior anomalous.
- 16.2.11 (breaker) — the report dates the damage to EVA prep (oxygen purge system impact); the crew discovered it after the EVA. The EVA-equipment concept’s current debrief-sourced wording (“working with the PLSS on the back… broke one circuit breaker”) is compatible but attributes the damage by inference.
The patterns the register shows
Section titled “The patterns the register shows”- Indication, not function. A large share of the entries are instrumentation or display failures with healthy hardware behind them: 16.1.4, 16.1.5, 16.1.8, 16.2.3, 16.2.7, 16.2.12, 16.2.14. The crew’s machines mostly worked; their gauges lied.
- Repeat offenders the report itself links: the pre-1967 terminal boards (16.1.2 ↔ 16.1.3), water loose in the suit loop (16.2.3 ↔ 16.2.13), and the marginal VOX setting behind both EVA voice anomalies (16.2.8 ↔ 16.2.9).
- The fixes are Apollo 12’s gains: integral SPS filters, no bacteria filter, Luminary 1B’s radar-interrupt fix, circuit-breaker guards, the redesigned RCU connector, lubricated rock-box latches — this register is effectively the ledger of changes carried from the first landing to the second.
- Nothing here cost the mission an objective. The EVA-adjacent items (16.2.6, 16.2.8/9, 16.2.11, 16.3.1–3) cost time and margin, not outcomes; the two open anomalies (16.1.10, 16.1.11) belong to the CSM and the mission’s final hours.
Sources
Section titled “Sources”- Apollo 11 Mission Report (MSC-00171) — §16 Anomaly Summary (printed pp. 16-1 – 16-23, figures 16-1…16-22; PDF pp. 280–323); all table content and quoted phrases
- Technical Crew Debriefing, Vol. 1 (§9–10) and Vol. 2 (§11–14 text layer; pp. 74–216 are image-only scans) — crew cross-checks
- Plan-vs-actual and the EVA planned-vs-actual concept — where the EVA-adjacent anomalies already surface in the library