BizAv Cockpit Upgrade Paths: Collins Pro Line 21

Ken Elliott explores different pathways for common business aircraft cockpit upgrades, this month reviewing the Collins Aerospace Pro Line 21 retrofit...

Ken Elliott  |  18th January 2024
    Back to Articles
    Ken Elliott
    Ken Elliott

    Ken Elliott is a veteran with 52 years of aviation experience, focussed on avionics in General and Business...

    Read More
    Collins Pro Line 21 Avionics Suite in Private Jet Cockpit

    During a potential pre-owned aircraft acquisition the primary avionics suite is inevitably a purchasing consideration. More than likely, the suite will originate from a single avionics’ provider that, in collaboration with the aircraft manufacturer, had tailored a specific electronic platform for each make and model of aircraft for which it was contracted.

    One common avionics suite that can be found in business aircraft is Collins Aerospace’s Pro Line 21. The staging of the Pro Line 21 avionics panel (see Figure A below) is mostly represented by:

    • Three or four large format displays (Primary Flight Displays - PFDs – and Multifunction Flight Displays – MFDs).
    • Display Control Panels (DCPs), to interact with the main displays.
    • Control Display Units (CDUs) to configure the Flight Management Systems (FMS) for navigation, plus selection of frequencies and modes to manage remote equipment. 

    Aircraft models evolve over time, and it is rare for the airframe manufacturer to commence from a clean sheet design. Modern aircraft manufacturers form alliances with suppliers and develop long-term relationships. Together, they will mock-up a cockpit, simulating realistic pilot experiences while conducting virtual flights.

    The primary avionics will advance over generations of progressive aircraft to accommodate new technologies, emerging airspace requirements and cater to ergonomic improvements.

    FIGURE 1: The Staging of Collins Aerospace's Pro Line 21 displays and controllers in a
    Bombardier Challenger 605 business jet

    For newer aircraft, irrespective of the avionics suite it should be noted that after delivery their avionics are not frozen in time. Service Bulletins (SBs) and Aircraft Service Changes (ASCs) are issued to undertake required and optional alterations as they arise. These include:

    • Correction of an in-service issue
    • Meeting changing airspace operation requirements
    • Accommodating product improvements
    • Installing existing available options, or
    • Installing newly-certified product options.

    For pre-owned aircraft, it is very common for the buyer to be faced with an aircraft that is still equipped with its original avionics package. Even though it should already be upgraded for operational mandates such as ADS-B Out, TCAS II Change 7, ELT, standby instruments and more, its primary equipage will remain the same.

    When a major upgrade – such as Pro Line 21 suite – is made available as an option, there is less incentive to invest in the potentially significant finance involved. However, when the displays face obsolescence or the owner is unable to meet an emerging airspace requirement, these circumstances necessitate an upgrade.

    All Pro Line 21 upgrades will be installed and certified either via an existing Supplemental Type Certificate (STC), or factory TC amendment. They will all consist of baseline equipment and multiple additional options.

    If you are considering such an upgrade it is important to know that the Pro Line 21 interfaces significantly with existing remote systems that must be compatible and may, themselves, require updating.

    Collins Aerospace Pro Line 21

    A long established, highly regarded provider of avionics, Collins Aerospace (formerly Rockwell Collins) produces the Pro Line 21. Commencing generations ago with Pro Line I analogue avionics, Collins has progressed through to digital avionics in the Pro Line 21 and the later Pro Line Fusion series.

    The predecessor of the Pro Line 21 is the Pro Line 4, and upgrades usually replace either a Pro Line 4 or earlier Pro Line II package.

    Collins has provided the Pro Line 21 as the primary avionics in new build aircraft, making it available for upgrade on pre-owned aircraft too. The Pro Line 21 is tailored to specific aircraft types and models that in some cases may be serial number specific.

    It is, therefore, recommended that you consult with your preferred avionics facility (that may also be the aircraft OEM) to ensure a Pro Line 21 offering is applicable to your aircraft, and that any additional requirements are included and priced.

    Keep in mind, too, that all equipment providers and shops that install avionics have been faced with procurement and labor challenges. Ensure you allow plenty of time for any major upgrade package, and if you’re purchasing a pre-owned aircraft, be prepared to take delivery first and then schedule an upgrade.

    How Pro Line 21 Works

    Viewing the Adaptive Flight Displays (AFDs) and entering data via the DCUs and CDUs, the pilot prepares for a flight by selecting trip details to navigate using the FMS. They set frequencies and modes to manage Communications, Navigation and Surveillance (CNS), select display modes for the onside AFDs and choose a flight control mode into a separate glareshield mounted controller.

    The AFDs help to declutter the cockpit and typically consist of four displays. The PFDs provide traditional, but much enhanced Flight Director (FD) and Horizontal Situation Indicator (HSI) data directly in front of the pilot(s), while the MFDs provide systems synoptic data, flight charts and route maps, graphical and XM weather and diagnostic pages.

    Reversionary switching is available between the various flight displays, as needed. Pro Line 21 AFDs are manufactured in different flavors, each with a dedicated part number. While earlier versions have image selections on the displays themselves, later versions are fully remote controlled from separate Display Control Panels (DCPs). 

    Model designations ending in ‘E’ have internal ethernet cards, essential for Integrated Flight Information System (IFIS) functionality.

    For many pilots, the operating differences between a Pro Line 4 and Pro Line 21 are not major. However, between the earlier Pro Line II and Pro Line 21 operation is significantly different, moving from analog to digital functionality.

    In either case, the remote avionics interfaced to the Pro Line 21 are much the same as before (in that CNS and flight controls remain operationally similar). It is having modern displays and the addition of new features that catch the attention of, and provide huge benefits to, flight crews.

    So, while the big draw is the cockpit displays, what they enable in additional features and electable options – including the ability to meet new operating requirements – can drive an upgrade decision.

    Pro Line II equipped aircraft included Line Replacement Units (LRUs) as dedicated hardware ‘boxes’ for each sub system, and some early aircraft are still equipped that way. Later aircraft were completed with module ‘cages’, housing ‘cards’ that individually serve as a sub-system.

    Data is transferred between systems on common ARINC busses, specialized by technology and given unique designations, such as ARINC 429. Data concentrators direct electronic traffic along the way.

    TABLE A: Matrix of Pro Line 21 Upgrade Options for Various Aircraft Types

    An Overview of Pro Line 21 Features

    Apart from new displays and their arrangement, there are several exclusive features available with a Pro Line 21 upgrade. Some are baseline and some optional.

    Pricing commences with the baseline package for each model of aircraft, then each available option is offered on an individual, additional fee basis. Bundling of options may sometimes be offered.

    Baseline Pro Line 21 Features

    • New cockpit displays (quantity is aircraft dependent).
    • Enhanced engine indication displayed on the new cockpit flight displays.
    • Increased database memory enabling greater scope of airport, airspace and other data, updated on regular basis. (Operators can also add a runway database as an option that requires an extra subscription. See Options for direct database update capability.)
    • Maintenance diagnostics.

    Navigation & Charting-related Baseline Features

        Integrated Flight Information System (IFIS) providing:
    -    Enhanced maps with airways, intersections and geopolitical boundaries
    -    Own ship position on electronic charts
    -    Split chart displays for improved chart coverage
    -    Satellite weather
    -    Chart-Link or e-Chart to FMS flight plans
    -    Geo-referenced airport diagram upon landing.

    • Flight Path Vector (FPV) – a HUD like feature on the flight director presentation that indicates the energy state of the landing aircraft.
    • FMS latest version (aircraft dependent).
    • Approach Path Vertical (APV) – a precision navigation landing procedure available for operations in Europe which also complies with Terrain Awareness Warning System (TAWS) Mode 5 monitoring requirements.
    • Lateral Path Vertical (LPV), a version of precision navigation landing procedure available for operations in the US, Europe and Canada, including operations using Wide Area Augmentation System (WAAS) GPS.
    • ZYX approaches, providing capability to utilize multiple similar approaches to the same runway, where each is designated using a letter Z, Y, X, in that order.
    • Integrated Receiver Autonomous Integrity Monitoring (RAIM) ensuring accuracy when using GPS navigation using GLONASS, GALILEO and GPS satellites.
    • FMS curved approaches using Required Navigation Performance (RNP) and Approval Required (AR) 0.3 – permitting expedited and direct runway access.
    • Ability to complete RNP 1, 2 and 4 navigation to meet enroute, terminal, oceanic and remote lateral limitations.
    • Navigation beyond North 73 and South 60 latitudes that may require the installation of an Inertial Reference System (IRS).

    Surveillance-related Baseline Features

    • Integrated Automatic Dependent Surveillance -Broadcast (ADS-B) annunciation – digital annunciation in the new displays removing remote analog annunciation. ADS-B is v2 (DO260B compliant).

    Optional Pro Line 21 Features

    The following optional Pro Line 21 features are available with additional equipment and integration, where all equipment is available from Collins Aerospace. Some aircraft will be delivered with options as baseline, and some options are not available for specific aircraft.

    Depending on the size, capability and operational scope of the aircraft, some options may be considered impractical.


    • Information Management System (IMS-3500, -6000, -6010) with Aircraft Information Manager (AIM). Enabling secure, remote and wireless data transfer.
    • Video capability on the new MFD(s). Suitable for externally supplied security cameras and heads-down enhanced vision displays.
    • Ability to add a third IFIS on some aircraft.
    • Crew Force Measurement (CFM) with the addition of control sensors to measure applied crew force in flight and send data to the onboard Flight Data Recorder (FDR).
    • Data Base Unit-5010E upgrade – for use with USB devices to update navigation and chart data.

    Communication-related Options

    • VHF datalink providing Controller Pilot Datalink Communications (CPDLC) capability, including Departure Clearance (DCL) and LINK 2000+ compatibility for Eurocontrol operations. A second datalink may be added.
    • Future Air Navigation System (FANS 1/A) over Viasat, for datalink and navigation in oceanic and remote areas. Note: Automatic Dependent Surveillance–Contract (ADS-C) requires the installation of a satellite system.
    • HF-9000 high frequency communications and datalink suitable for oceanic and remote operations.
    • Satellite communication and cockpit connectivity via both Iridium and Inmarsat (now Viasat).

    Navigation & Charting-related Options

    • Additional FMS/GPS where aircraft is currently equipped with single systems.
    • Head-Up Display(s) with head-up Enhanced Vision System (HUD-EVS or EFVS), available for some aircraft.
    • Synthetic Vision Systems (SVSs) for situational awareness and aid to navigation. (May add a second system.)
    • Wide Area Augmentation System – Lateral Path Vertical (WAAS-LPV) for GPS approaches, popular with Business Aviation at regional and local airports.
    • Steep approaches for specific airport operations.
    • Surface Movement System (SMS) for situational awareness, movement on airports, and take-off and landing. 

    Surveillance-related Options

    • Traffic Collision Avoidance System (where not already installed) and an upgrade to Version 7.1 (required for international operations and recommended elsewhere).
    • Multi-scan Threat Detection System radar, with extended range and turbulence avoidance.
    • XM satellite weather (North America) – requiring additional aircraft installation, including top antenna placement. May add a second XM weather system.
    • ARINC graphical weather (worldwide), available when communications datalink is installed.
    • Quick Access Recorder (QAR) to save and download flight and engine performance data.

    Note: ADS-B Out Version 2 is an option but should by now be installed on aircraft as its mandate date has passed in most regions. Check that your ADS-B solution is Version 2.

    Additional options for cabin and connectivity:

    • Inmarsat (now Viasat) Jet ConneX, SwiftBroadband and Viasat HS internet.
    • Iridium voice and fax.
    • Venue Cabin Management System (CMS).
    • Stage (content-streaming server).
    • Tailwind satellite television.
    • Airshow moving maps, flight information and mobile content.

    Additional options for flight support:

    • Corporate Aircraft Service Program (CASP), a post-delivery product support service program.
    • ARINCDirect

    -    International trip support
    -    Flight Operations System (FOS)
    -    Flight planning
    -    Connectivity services.

    Pro Line 21 Upgrade Considerations

    For any major avionics upgrade, each type and model of business jet will have unique characteristics that could be as simple as the level of software in a specific avionics system.

    Once an aircraft has delivered, it will begin to develop its own history and may undergo modifications, improvements and additions that other aircraft of an identical build, don’t.

    Further, aircraft manufacturers will ‘cut in’ changes to avionics during a production run, such that from a certain serial number forward, the change becomes standard. That change may also be available as an optional service bulletin or modification to earlier serial numbers.

    FIGURE 2: Various Remote Pro Line 21 Avionics and Aircraft Systems

    Each of the previous situations can impact a major avionics upgrade in the following ways:

    • System pricing
    • Installation fee
    • Downtime
    • Certification
    • Operational capability
    • Available features
    • Limitations.

    To reiterate, it is very common to encounter situations where an upgrade, as promoted, is not one-size-fits-all. For this reason, pricing, downtime and certification cannot be assumed.

    It is more important to try to approach your preferred service center with adequate information, enabling them to provide an accurate estimate, and to forewarn you of potential issues including extra downtime or costs.

    When estimating a PL-21 upgrade, the salesperson will typically engage engineering, certification and other specialists to ensure nothing is overlooked. Compatibility of existing avionics is of paramount importance, and although the model of a sub-system may be correct, its part number or modification status (either hardware or software), may not be.

    Some of the key pieces of information most useful to the service center for quoting and completing an upgrade are to know your existing equipment. You should be able to produce part numbers, serial numbers, modification, and software level of all dedicated hardware. This is facilitated by up-to-date aircraft logbooks, modification records and equipment lists.

    Maintain your certification records. Since delivery, any change to your aircraft should be accompanied by applicable certification data – from wiring diagrams to repair or service bulletin records. These should be retained by operators, ready to share with a service center.

    The service center should also be given a clear picture of what options you may need, based on your specific way of operating the aircraft, such as oceanic, remote, specific region, airports and routes. Do not expect the service center to automatically know your unique requirements.

    Keep in mind that it is best to only open an aircraft’s interior once, reducing overall downtime and cost. If you can include any available option because it is convenient, do so. It will enhance the resale value and capability of your aircraft.

    As stated, the flight crew interact with the Pro Line 21 primarily through DCUs and CDUs, while viewing current flight information on the AFDs. However, consider that a significant quantity of new, and mostly existing, remote equipage drives off, or takes instruction from, the Pro Line 21.

    There is deep complexity to business aircraft electronics, and both electrical and certification engineers have much due diligence to review prior to, and in support of, an upgrade.

    In Summary...

    Lastly, cockpit upgrades as significant as the Pro Line 21, can involve both time and some disruption. Many operators use the opportunity to add cabin updates and aircraft paint work. It will be sensible to at least consider some of the Collins cabin offerings listed previously.

    The Pro Line 21 is a proven, reliable, well supported and popular aircraft upgrade. Collins Aerospace has the experience, the technology and the reputation to proudly stand behind each Pro Line 21 upgrade.

    Do you have a specific aircraft maintenance, upgrade or repair need?

    Use Advantage to outline your maintenance requirements by completing our quick form, and your enquiry will be passed to qualified service providers. Receive the feedback you need to help you choose the right partner and the best deal.
    Start now

    Related Articles



    Other Articles

    Need Avionics Services?

    Use AvBuyer’s Maintenance/ Upgrade Locator Service todayConnect now
    Bombardier Challenger 350
    Please call
    Cessna Citation CJ3
    Price: USD $5,595,000 Price Reduced
    Dassault Falcon 900LX
    Off market
    Gulfstream G550
    Price: USD $15,500,000 Price Reduced
    Hawker 800XP
    Make offer
    Cessna Citation Bravo
    Make offer
    United States - FL
    Cessna Citation XLS
    Please call
    United States - VT
    Cessna Citation 500
    Please call
    United States - OR
    Gulfstream G650ER
    Please email
    Aero Commander 695A
    Price: USD $1,800,000 Excl. VAT
    South Africa
    Boeing BBJ
    Make offer
    Bombardier Global Express
    Price: USD $10,500,000
    Pilatus PC-12 NG
    Price: USD $4,200,000 Excl. VAT, Price Reduced
    United Kingdom - England
    Bombardier Challenger 850
    Price: USD $6,900,000 Price Reduced
    United States - FL
    Hawker 400XP
    Price: USD $2,680,000
    McDonnell Douglas MD-87
    Make offer
    United Arab Emirates
    Boeing BBJ
    Please call
    Embraer Legacy 450
    Price: USD $12,500,000 Price Reduced
    United Kingdom - England
    Cessna Citation CJ2+
    Price: USD $4,550,000 Price Reduced
    Gulfstream G450
    Make offer
    United States - CA
    loder image