Fortran for Aerospace: How to Document 30-Year-Old Flight Calculations

The most dangerous code in the world isn't a zero-day exploit; it’s a 30-year-old Fortran routine that works perfectly, but no one alive understands why. In the aerospace sector, these "ghosts in the machine" handle critical flight calculations, trajectory modeling, and sensor fusion. When you are tasked to fortran aerospace document 30yearold systems, you aren't just writing a manual—you are performing digital archaeology on $3.6 trillion of global technical debt.

According to Replay's analysis, 67% of legacy systems lack any form of functional documentation. In aerospace, where a single miscalculated decimal point in a trajectory algorithm can result in catastrophic failure, the stakes of undocumented code are existential. We no longer have the luxury of 18-month manual rewrite cycles. We need a way to extract the business logic from the UI down, capturing the "as-is" state of these systems before the last engineers who understand them retire.

TL;DR: Documenting 30-year-old Fortran aerospace calculations is a high-risk manual process that typically takes 40 hours per screen. By using Replay, teams leverage Visual Reverse Engineering to convert recorded user workflows into documented React components and Design Systems, reducing modernization timelines by 70% and turning "black box" calculations into readable, modern code.

The $3.6 Trillion Technical Debt in Aerospace#

The aerospace industry is built on the shoulders of Fortran (Formula Translation). While the language is incredibly efficient for numerical computation, the surrounding infrastructure—the terminal interfaces, the batch processing scripts, and the lack of modularity—is a bottleneck for modern digital transformation.

Industry experts recommend that before any migration begins, a comprehensive "Flow Map" of the existing system must be created. However, manual documentation is a failing strategy. Statistics show that 70% of legacy rewrites fail or exceed their timelines because the requirements were misunderstood during the documentation phase.

Video-to-code is the process of capturing real-time user interactions with a legacy system and using AI-driven visual analysis to generate functional specifications, component architectures, and modern UI code.

Why You Must Document 30-Year-Old Fortran Aerospace Systems Now#

The urgency to fortran aerospace document 30yearold logic stems from three primary pressures:

1. •The Talent Gap: The engineers who wrote the original flight dynamics libraries in the 1980s and 90s are retiring.
2. •Regulatory Compliance: Modern FAA and EASA standards require a level of traceability that 30-year-old codebases simply cannot provide without massive manual effort.
3. •Cloud Migration: You cannot move a "black box" to the cloud. You must first understand the inputs, outputs, and side effects of every calculation.

Replay addresses these pressures by providing a platform where a subject matter expert (SME) simply records themselves performing a flight calculation workflow. Replay’s AI then deconstructs the visual changes on the screen to infer the underlying data structures and logic.

Manual Documentation vs. Visual Reverse Engineering#

The traditional approach to document a 30-year-old system involves a developer sitting with an SME, taking notes, and trying to read through thousands of lines of Fortran 77 or 90. This is prone to "hallucinated requirements" where the developer assumes the code does something it doesn't.

The Implementation: Converting Fortran Logic into React Components#

When we talk about how to fortran aerospace document 30yearold calculations, we are looking for the "Source of Truth." In many aerospace applications, the UI is a terminal emulator or a thick-client Java/C++ wrapper around Fortran kernels.

By recording these workflows in Replay, you generate a "Blueprint." This Blueprint identifies that a specific input field on a 1994-era screen corresponds to a "Fuel Flow Coefficient" and that the resulting output is a "Thrust-to-Weight Ratio."

Here is how we represent a legacy aerospace calculation input as a modern, documented React component using TypeScript:

typescript
// Generated via Replay Blueprint Editor
import React, { useState, useEffect } from 'react';

interface TrajectoryInputProps {
  initialVelocity: number;
  launchAngle: number; // Degrees
  onCalculate: (result: FlightResult) => void;
}

interface FlightResult {
  maxAltitude: number;
  downrangeDistance: number;
  timeOfFlight: number;
}

/**
 * @description Modernized interface for legacy FORTRAN 'TRAJ_CALC_SUB' routine.
 * Original Source: SRC/FLIGHT/CALC_V1.FOR
 * Documentation Date: 2024-10-25
 */
export const TrajectoryCalculator: React.FC<TrajectoryInputProps> = ({
  initialVelocity,
  launchAngle,
  onCalculate
}) => {
  const [loading, setLoading] = useState(false);

  const handleRunCalculation = async () => {
    setLoading(true);
    // In a modernized stack, this calls a WASM-compiled Fortran module 
    // or a rewritten Go/Python microservice.
    const result = await legacyFlightEngine.calculate(initialVelocity, launchAngle);
    onCalculate(result);
    setLoading(false);
  };

  return (
    <div className="p-6 bg-slate-900 text-white rounded-lg border border-blue-500">
      <h3 className="text-xl font-bold mb-4">Flight Path Parameters</h3>
      <div className="grid grid-cols-2 gap-4">
        <label>Initial Velocity (m/s): {initialVelocity}</label>
        <label>Launch Angle: {launchAngle}°</label>
      </div>
      <button 
        onClick={handleRunCalculation}
        className="mt-4 px-4 py-2 bg-blue-600 hover:bg-blue-700 rounded"
      >
        {loading ? 'Processing Fortran Kernel...' : 'Execute Calculation'}
      </button>
    </div>
  );
};

Mapping the Workflow: From Video to Flow#

The core of the Replay platform is the "Flows" feature. When you record a session of an engineer using a 30-year-old aerospace tool, Replay doesn't just see pixels. It sees state changes.

1. •Recording: The SME records the process of entering atmospheric data.
2. •Extraction: Replay identifies the UI patterns—the tables, the input fields, the "calculate" buttons.
3. •Documentation: The AI generates a technical specification that maps the visual UI to the Fortran logic.

This process is critical when you need to document legacy systems that have no existing architectural diagrams.

Bridging the Gap: From Fortran Aerospace Logic to Modern React Components#

The hardest part of trying to fortran aerospace document 30yearold systems is the data transformation. Fortran often uses flat files or proprietary binary formats for input/output. A modern React frontend needs JSON.

According to Replay's analysis, the average enterprise rewrite takes 18 months because developers spend 50% of their time just trying to map data types. Replay's AI Automation Suite suggests data interfaces based on the visual output of the legacy system.

Here is a TypeScript definition of what a documented Fortran data structure looks like once extracted via Replay:

typescript
/**
 * @interface LegacyAerospaceData
 * @description Extracted from 30-year-old telemetry dashboard.
 * Maps to COMMON /BLOCK/ in Fortran source.
 */
export interface LegacyAerospaceData {
  /** @format real*8 - Double precision float */
  telemetry_id: string;
  
  /** @unit Kelvin - Stored as offset from 0 in legacy */
  exhaust_gas_temp: number;
  
  /** @unit PSI - Pressure sensor 04 */
  internal_pressure: number;
  
  /** 
   * Validation logic extracted from UI behavior:
   * If value > 1500, UI triggers "OVERHEAT" warning.
   */
  status: 'NOMINAL' | 'WARNING' | 'CRITICAL';
}

By defining these interfaces early, you can build a Design System that reflects the actual utility of the legacy system while providing a modern user experience.

Security and Compliance in Regulated Aerospace Environments#

Aerospace is one of the most highly regulated industries on earth. You cannot simply upload screen recordings of flight calculations to a public cloud. Replay is built for these environments, offering:

• •SOC2 & HIPAA Readiness: Ensuring data integrity and privacy.
• •On-Premise Deployment: Run the entire Visual Reverse Engineering suite behind your firewall, ensuring no sensitive flight data ever leaves your secure network.
• •Air-Gapped Support: For defense-related aerospace projects, Replay can operate in completely disconnected environments.

When you fortran aerospace document 30yearold calculations, you aren't just looking for the math; you're looking for the edge cases. Replay captures the error states—what happens when the user enters an out-of-bounds value? These "negative paths" are rarely documented in 30-year-old manuals but are captured perfectly in a Replay recording.

The 70% Time Savings: A Reality Check#

Is it really possible to save 70% of the time? Let’s look at the math.

A typical aerospace dashboard might have 50 screens.

• •Manual Method: 50 screens x 40 hours/screen = 2,000 hours. At $150/hr, that’s $300,000 just for documentation.
• •Replay Method: 50 screens x 4 hours/screen = 200 hours. At $150/hr, that’s $30,000.

The savings aren't just in the documentation; they are in the accuracy. Because Replay generates documented React code directly from the visual truth of the legacy system, the "Discovery Phase" of the project is compressed from months into weeks.

Frequently Asked Questions#

How does Replay handle terminal-based Fortran interfaces?#

Replay's Visual Reverse Engineering engine is designed to recognize text-based patterns and terminal layouts. It treats the terminal output as a structured data source, identifying prompts, inputs, and tabular data, which it then maps to modern React components and JSON schemas.

Can we document calculations that don't have a UI?#

While Replay is a visual-first platform, most 30-year-old aerospace systems have some form of operator interface, even if it is a command-line tool. By recording the interaction with these tools, Replay captures the relationship between inputs and outputs, which is the foundation of documenting the underlying Fortran logic.

Is the code generated by Replay production-ready?#

Replay generates highly accurate React components, Design Systems, and Blueprints. While we recommend a human-in-the-loop review for critical flight safety systems, the generated code serves as a 90% complete foundation, drastically reducing the manual coding effort.

How do you handle the high-precision requirements of Fortran in React?#

Fortran's

or math is often more precise than standard JavaScript numbers. When Replay documents these systems, it flags high-precision fields in the generated TypeScript interfaces, allowing developers to implement BigInt or specialized math libraries (like Decimal.js) to maintain calculation integrity.

What industries besides aerospace use this for legacy documentation?#

Beyond aerospace, Replay is used in Financial Services for COBOL modernization, Healthcare for legacy EHR systems, and Government for decades-old tax processing systems. Any industry with massive technical debt and a lack of documentation benefits from Visual Reverse Engineering.

Conclusion: Stop Guessing, Start Recording#

The mission to fortran aerospace document 30yearold flight calculations is too important to leave to manual note-taking and guesswork. The risk of losing institutional knowledge is too high, and the cost of failure is too great.

By leveraging Visual Reverse Engineering, aerospace enterprises can finally see inside the "black box" of their legacy Fortran systems. You can turn 30 years of undocumented math into a living, breathing Design System and a library of modern React components.

Ready to modernize without rewriting? Book a pilot with Replay