In-cockpit weather displays

This element is about the digital displays in modern cockpits — what they show, what they don't, and the strategic vs. tactical operating principle that keeps the data useful without becoming misleading.

Strategic awareness, not tactical truth. The picture on your tablet is real, but it's also old — and the value of every datalink product depends on knowing exactly how old.

Inflight datalinks

Two services dominate.

FIS-B

• Flight Information Service-Broadcast, FAA-provided over the 978 MHz UAT ADS-B link
• Free
• Requires ADS-B In on 978 UAT
• Ground-station based; generally above ~1,500 ft AGL in CONUS, less in mountains, none in remote or oceanic regions
• Authority and product list per AIM 7-1-10

Products broadcast: METARs, SPECIs, TAFs, AIRMETs, SIGMETs, Convective SIGMETs, PIREPs, winds and temps aloft, TFRs, NOTAMs (D and FDC), SUA status, NEXRAD CONUS and regional, Center Weather Advisories.

Not on standard FIS-B: lightning, satellite imagery, some graphical hazard overlays.

SiriusXM Aviation

• Satellite-based subscription service
• Roughly $30–100/month
• Requires an XM Aviation receiver
• Full CONUS, parts of Canada and Mexico, no altitude floor
• Latency generally lower than FIS-B; NEXRAD typically 2–5 min vs. FIS-B's 5–15+ min
• Subscription lapses and heavy convection blocking the antenna are the failure modes

Adds to the FIS-B list: lightning strikes, storm cell tracks, satellite imagery, higher-frequency NEXRAD updates.

NEXRAD latency

The single most important concept on this element §info-18007. The radar mosaic on your EFB looks live, but isn't.

• Radar scan — 4–6 minutes per volume sweep
• Mosaic processing and broadcast add more delay
• Total age on display — typically 5–15 minutes, sometimes more
• The displayed timestamp is BROADCAST age, not radar scan age — the underlying scan is older

A fast-moving cell can travel several miles in 10 minutes. The rule:

Use NEXRAD strategically. Use eyeballs, ATC, and PIREPs tactically.

Strategic = "go around the line, divert clear of the system." Tactical = "pick a path between cells." The first is appropriate for datalink. The second is not.

ADS-B In traffic

The traffic display on your EFB has gaps you need to understand.

• ADS-B Out aircraft — visible directly, ADS-B-to-ADS-B
• Non-ADS-B aircraft — only via TIS-B (Traffic Information Service - Broadcast), which is ATC radar tracks rebroadcast over ADS-B
• TIS-B trigger envelope — your aircraft must be in ATC radar coverage AND another ADS-B Out aircraft must be within ~15 NM to trigger the broadcast
• Outside that envelope — non-ADS-B traffic may not appear, even when it's near you
• ADS-R — bridges 978 UAT and 1090ES traffic across the two links
• Ghost targets — your own ADS-B Out can appear as TIS-B traffic if misconfigured

See-and-avoid is the primary tool §91.113. Datalink traffic is supplementary.

EFB apps and currency

Modern cockpits display weather and aeronautical info on EFB apps (ForeFlight, Garmin Pilot, FltPlan Go) or integrated avionics (Garmin G1000/G3X/GTN, Avidyne IFD, Dynon SkyView).

What's on the display

• Moving map with terrain, obstacles, airspace
• ADS-B In traffic — TIS-B plus ADS-R bridge
• Charts — sectional, IFR, approach plates
• Airport info — METAR/TAF overlay, frequencies, fuel, runways
• TFRs and SUA — shaded on the map
• NOTAMs by airport

What makes the display authoritative

A digital display's authority is only as good as its underlying data:

• Chart subscription — current per Part 91; check the cycle date
• Database currency — for IFR avionics, the navigation database must be current per the operator's regulatory framework
• App sync — when did the EFB last download updates? Lapsed subscription means no auto-update
• Datalink coverage — FIS-B below ~1,500 AGL or in remote areas; SiriusXM at end of subscription

Failure modes to anticipate

• Attention sink — rich displays pull eyes inside the cockpit at the cost of see-and-avoid scanning
• False authority — moving maps and live-feeling NEXRAD encourage tactical decisions the data can't actually support
• Single-point failure — overheating iPads, dead batteries, connection drops; carry a backup device or paper

Currency check before flight: open the EFB, verify chart cycle, subscription status, and recent sync.

Strategic vs. tactical

Cockpit displays of digital weather are intended to supplement preflight briefings and pilot judgment, not replace them AC 00-63.

• Strategic (NEXRAD trend, METAR/TAF trend, AIRMETs and SIGMETs) — route around a system, plan a divert, choose a holding airport
• Tactical (eyeballs, ATC, PIREPs, onboard weather radar where equipped) — pick a path between cells, time a hole in a line
• Verification — out-the-window observation overrides the display every time

Worked examples:

• NEXRAD over a developing line. The mosaic on the EFB shows a line of cells 30 NM ahead with a clean gap on the south end. The most recent broadcast timestamp reads 6 minutes old. Per §info-18007, the actual scan underneath is older — potentially 10–15 minutes by the time you see it. A cell moving 40 KT covers 7–10 NM in that window — the "clean gap" may have already closed. Strategic move: deviate 20 NM around the south end, or delay/divert. Tactical "thread the gap" is not supported by the data.
• EFB traffic with one VFR target missing. The display shows a Class E corridor clean of traffic. You're outside ATC radar coverage (low altitude in a remote area), so TIS-B isn't broadcasting from ATC tracks. A non-ADS-B VFR aircraft 2 NM behind you at your altitude is invisible to the display. See-and-avoid is still primary §91.113 — an empty traffic display is not the same as empty airspace.