Comac's next import substitution target is the sealant drum, not the engine

An aerospace sealant is not hard to formulate. Getting it onto an approved materials list, and keeping it there across the service life of an airframe, is the hard part, and it is also the part that pays: every drum sold after qualification is reorder business nobody has to win again. That is the layer of the C919 that Chinese suppliers have now been pointed at ^[1].

The engine is still the conspicuous dependency. The CJ-1000 remains under development at the Aero Engine Corporation of China and is meant to become a domestic alternative to the Leap-1C, which is for now the only engine a C919 can fly with, and which is built by CFM International, the GE Aerospace and Safran joint venture ^[7][8]. So on engines the number of qualified sources is one ^[1]. The consumables programme is not waiting for that to change.

What makes the account credible is that it concedes the gap. Zhang Xiaoyan said of Western materials that "their products are reliable and have truly stood the test of time" ^[9], and specialised cleaning agents imported from Western suppliers are reportedly still needed for some engine maintenance work ^[11]. The stated aim is a backup source rather than an immediate exit ^[17], and displacing established products is expected to take years ^[18]. Read as procurement rather than politics, that is a plan to hold two qualified sources on a materials list, which is a different thing from switching.

The shortcut China is reaching for is military. Zhang said anticorrosive coatings, adhesives and chemical buffering agents developed for military aircraft could be adapted to civil programmes, including the C919 and the C929 widebody still in development ^[12]. Existing production experience is the scarce input here, and defence work is where China already has it.

The awkwardness sits with the regulator. Zhang rejected the suggestion that substitutions could damage the C919's European certification effort, saying Comac had considered the matter and that "it will not create any adverse impact. We are simply providing an additional safeguard with the option of domestic products" ^[13]. Certification is not expected soon, because regulators still have to analyse flight data and finish further technical work ^[15]. Domestic materials are already on test aircraft while that review is open ^[2], and whether a second qualified sealant counts as an additional safeguard or a design change is not Comac's call to make.

Scale keeps this from being an immediate revenue event: Comac had delivered 42 C919s to Chinese customers by July, against service entry in May 2023 ^[5]. Consumables demand tracks fleet hours, and 42 airframes is not much of a fleet. The qualification position is the asset, and it is being contested now, years before the volume arrives.