About the HOGE Calculator
The HOGE Calculator by Linth Air Service AG (helicopter flight school and operator in Mollis, Glarus, Switzerland) is a free online flight preparation tool for helicopter pilots, student pilots and flight instructors. It calculates hover performance HOGE (hover out of ground effect) and HIGE (hover in ground effect) directly from the digitised flight manual charts and combines it with a complete mass & balance calculation.
- Performance: maximum weight, maximum fuel and margin to the landing weight per landing site and temperature (ISA scenarios or measured OAT); pressure altitude from site elevation and QNH; every value with its calculation steps and a check in the original manufacturer chart.
- Mass & balance: longitudinal and lateral CG for zero fuel, take-off and landing, envelope diagrams, load sheet and load manifest as PDF; empty weight and empty CG from your own weighing report, plus additional items with their own arm.
- Helicopter types: Airbus H125 / AS350 B3e (also with SUP.27 Increased Takeoff Power and SUP.28 2370 kg), Airbus EC120B (H120), Guimbal Cabri G2 and MD Helicopters MD902 Explorer (PW206E/PW207E, with Category A WAT limits and a dedicated ‘Cat A’ tab: Category A take-off and landing at a known site as a checklist in accordance with RFM Section XI and EASA PC1, with profile and plan view) – Linth Air Service fleet or your own helicopter with your own values.
- Landing sites: all 40 mountain landing sites in Switzerland (FOCA) and further sites from the Linth Air Service mountain flying training (MOU); custom sites with elevation in ft or m.
- Runs in the browser on PC, iPad and phone, also offline; inputs stay local in the browser.
Important
Training and planning aid of the Linth Air Service ATO – not an approved performance or mass & balance tool.
The flight manual and the current weighing report are authoritative. Before every flight, verify against the original FLM, the current QNH and the actual OAT.
The chart conditions apply (e.g. no wind, max. takeoff power) – never count wind as a reserve.
Performance (HOGE/HIGE)
- Pressure altitude: site elevation is converted to pressure altitude with the QNH according to ISA (approx. 26–27 ft per hPa). Without a QNH, 1013 hPa is used. ISA deviations refer to the pressure altitude of the site.
- Reading: digitised manufacturer charts; linear interpolation between two OAT curves. Warmer than the warmest curve → ‘outside chart’. Colder than the coldest visible curve → the next colder curve is extended linearly (conservative). Values rounded down to 5 kg.
- * = at the weight limit: the limiting factor is weight, not performance.
- Fuel max. = max. weight − ZFW, at most the tank capacity; if fuel is entered in litres, also shown in litres (rounded down). Margin = max. weight − landing weight: ≥ 20 kg 0 … 20 kg negative
- Optional OAT per site adds an extra column ‘OAT at site’.
- Alt Penalty (Cabri): the chart is read at Hp + penalty, the OAT remains the actual one. LAS internal safety margin, because the Cabri chart is too optimistic at high temperatures – not part of the flight manual.
- Checking: every cell step by step in the calculation; show construction lines in the manufacturer chart; ‘FLM example’ recalculates the worked example from the manual; tapping the chart shows the OAT of that point (for H125 charts: tap the magenta ISA+35 line → the app must show ≈ ISA+35).
- EC120B HIGE is released for manual reading only.
Mass & Balance
- CG = sum of moments ÷ sum of weights; moment = weight × arm. Arms in m from the datum; lateral: right is positive.
- Checks cover zero fuel, take-off, landing and the transition in between (fuel consumption), min./max. weight, baggage compartment maxima, landing fuel ≥ 0 and fuel ≤ tank. For the H125 with SUP.28, additionally the lateral CG at landing above 2,250 kg (±0.08 m).
- Seat map: plan view to scale based on the three-view drawing in the FLM; seats, baggage, fuel and rotor at their FLM arms. Green = permissible CG at the take-off weight (longitudinal × lateral envelope).
- Dual controls: depending on the weighing, included in the empty weight or as payload (EC120B 5 kg / 1.99 m, H125 3.44 kg / 1.66 m). On the Cabri HB-ZZG they are included in the empty weight and cannot be switched (the weight for removal is not stated in the RFM).
- Adjust (temporary): empty weight and empty CG can be overridden (applies only in this browser; ‘Reset’ restores the weighing report). Additional items with their own weight and arm X/Y (e.g. cargo basket, ballast; negative weight = removed) also count as payload in the Performance tab.
- Fuel Burn is a guide value (EC120B 95, H125 145, Cabri 28 kg/h) – adjust it for each helicopter. Landing fuel = T/O fuel − trip (trip time × fuel burn, or trip fuel). Take-off and landing are linked: entering take-off fuel calculates landing fuel and vice versa; the field entered last (marked blue) stays fixed when the trip changes.
- Linked with Performance: same list of persons (seats are assigned in order), baggage total = sum of baggage compartments, ‘Fuel at landing’ = landing fuel.
- Load manifest: PDF with flight data, persons, load sheet, charts, performance reference and PIC signature.
Using the app
- Inputs are stored only locally in this browser – no data is sent to a server. ‘Reset’ clears everything.
- Works offline (after first opening it via the link) and on phone, iPad and PC. On the iPad: ‘Add to Home Screen’.
- A link with
#beispiel loads a performance example, #mb opens mass & balance, #beispiel-mb an M&B example.
