TPA - D.H.88 Comet - Freeware Released!

With the initial release of the comet now completed, if feel it might be worth updating this first post to make a link to the download for the freeware version easy to find!

D.H.88 Comet Freeware Download

Please do read through some of my more recent posts, or the freeware release page to have a better understanding of it’s development stage and what it can/cant do and how she now looks!

Hi all,

Today I feel I should formally introduce my current project for MSFS to everyone - the De Havilland D.H.88 Comet. Purpose built for the MacRobertson Air Race of 1934, the comet was Britain’s answer to winning the most extreme endurance race on the planet. While I am in the very early stages of development for this project to be truly finished, today marks 88 days before the 88th anniversary of the comet’s first flight.

The current plan is to release the aircraft in several stages, the first of which will be an entirely freeware version of the aircraft. The comet is an iconic piece of British engineering from the interwar period, introducing many new ideas and techniques which went on to help shape de Havilland’s future in aviation - as such I feel its important for as many people to experience it as possible! However, to come clean and be realistic about it, this is the first ever piece of 3d modelling work I have ever done, the first flight model I’ve ever created, and the first set of textures I have produced for an entire aircraft from scratch. It will take longer than I expect and I aim to produce a good quality product, rather some cobbled together junk! As a result, i have to be realistic about either the time-scale of this project, or the stages of quality i should aim to achieve at each release stage.

My hope is that by the 88th anniversary of the first flight of the comet (8th September 2022), i will have got the project to a point where i have a fairly well-modelled, and cleanly textured exterior model, with a decent feeling flight model, and a basic non-prototype interior cockpit. At whatever point i reach this i will be more than happy to release it as a freeware addon mod for anyone to install and enjoy. This will by no means be the final product however! I will continue to improve and develop the project as a freeware, working on the flight model to get it closer to true values, improve the texturing for the exterior and make a (more) realistic interior for her.

Alongside this, i will start refining the aircraft systems in as much depth as i feel i can using the SDK, as well as producing additional details and features both for the exterior and interior models to try and catch the glamour and charm of the original 1934 machines. These additional features i currently plan to add to build a pay ware version of the Comet for those wanting a more in-depth experience of even higher quality. This would be again updated over time, with the hope that income from the project could help pay for custom sounds/ additional details around the aircraft. I am fully aware that i am a nobody in terms of sim developers and accept that very little, if any of you will have faith on me hitting my goals! But we can all dream cant we? (also, i’d be asking pittance for a pay ware as i know it shouldn’t really be able to hold a candle to some of the amazing releases out there (looking at you 247D - even if they couldn’t get to the podium!)).

I originally started work on this project back in February of this year, i work full-time teaching in a secondary school in the UK, and have a 1 y/o daughter to look after, so the vast majority of this project has been completed between 10pm-1am on the odd days i can drag myself onto the computer. So it’s been slow and steady work! On top of this, i have another one due on the 12th of September, so i have no clue how development is going to work out after my initial target date. That being said, so far i have achieved:
A good representation of the wings, tail, and nacelles, with fully animated main gear, and a well-represented (from the front and side at least!) model of the Gipsy Six Series I R engine. I have also produced a fairly well convincing flight model, giving her the correct cruise and stall behaviours as stated by the flight tests and descriptions given by current pilots.

What i do need to do still is finish off the cockpit area of the fuselage, flaps, tail skid and central wing box. Whereby i will be happy with the modelling of the exterior model! I will make a VERY rough and ready interior space with a minimum of gauges to help fly, before focusing on texturing the exterior of the model to at least make her look good on camera! Given the speed of development so far, i suspect this will be more than enough to keep me busy up to and probably beyond the 8th September.

In advance to some comments, I suspect will be made in the future by prospective pilots… An issue I have kept running into is that pretty much all data given for the 88 from its original flights are described in British imperial units and mph, rather than US imperial and kts. This has meant already a number of modifications to get it to the correct specifications and weights! Particularly trying to get the correct fuel consumptions and MTOW! Alongside this, a large number of images of G-ACSS have been confused online with the American replica NX88D which has made it a bit of work trying to see if I’m actually following the correct designs or not… As for prototypical images from the correct era, the 88 was a racing machine in such high demand, she was changed countless times, with what appears to be very little available records of these changes. And despite the cockpit being where the pilots spent those exhausting 70 hours and 54 minutes, no one really seemed to care about what it looked like in there! As a result, I am planning to follow the few images I have of the original layout, but will obviously take some form of artistic license for it! I am also definitely going to be giving it a basic autopilot to allow us to do some long-haul runs without destroying our brains by sitting at our screens for 7 hours without a break, my current plan is to have the co-pilot position to house any sim-specific switches, radios and the autopilot panel. The idea being that it’s easily accessible and useable, but doesn’t ruin the idea of flying a 1934 classic.

I will aim to update this thread with my progress every week or so - or when i have completed something of minor note! I would also be greatly appreciative of feedback/ideas/support when it comes to reference material, or texturing of the aircraft. I have slowly been building up information myself, but knowing the flight sim community, and the historical popularity of this aircraft i wouldn’t be surprised if there are loads of you out there who know every nut and bolt of this beauty!

On a complete aside – I think it’s fairly lucky that 88 days before the first flight of an endurance champion of the same class, is also the 99th anniversary of motor racing’s most prestigious endurance race!

Edit: It’s been a long time since posting any images here… had rubbish quality so uploaded some larger ones so it doesn’t look like rubbish!


I regret that I have but one like to give.


Firstly huge congratulations for actually giving it a go. The progress you have made is superb!

On fuel flow I have some very recent experience. I have been helping to beta test a famous British Jet fighter over the last 6 months or so. Like you, conversion to imperial gallons from US. The the fact that the aircraft in question uses AVTAG rather than A1 which has a different density. So for example, 100 USG converted to IMP and the multiplied by 7.7 to convert the Imperial gallons of AVTAG to lbs.

I built a little table in excel to work out the fuel flow factor for a give altitude at standard air density assuming standard pressure etc.

I was getting almost exactly on the numbers at 7000 rpm, however there seems to be an oddity in the sim, because at higher rpm, the fuel flow decreases and at lower rpm it increases, which is clearly wrong.

Having spent weeks going round the houses, we settled on having the accurate numbers at 7000, and accepted that at other rpm it was out of our hands, but the table could be used to set the multiplication factor for a given rpm. Having said all that, that is for a turbine engine and it’s different for pistons.

That’s great news indeed. Thank you very much for your work!
This could and, given MFS’ history, should have been one of the first Local Legends or Famous Flyer aircraft.


I think that you’ve made a great start.

Well done :slightly_smiling_face:

This looks really exciting! Looking forward to seeing things progress!

Well done, this sounds like a very worthwhile project.

Have you considered contacting the Shuttleworth Trust at Old Warden airfield in the UK, as they own and still operate GACSS.

As far as flying the aircraft is concerned. I worked at Hatfield during the period that GACSS was rebuilt and test flown. I believe it is fair to say that the aircraft was not easy to fly, in particular the ground handling and take off and landings seemed to cause problems, even for the BAe test pilots. This culminated in a ground loop and undercarriage leg collapse when the aircraft landed at the end of its last flying display at Hatfield. The test pilot involved was extremely experienced and also flew the Mosquito, and I believe the decision was then made that trying to operate from runways, with crosswinds was not viable and operating from grass airfields into wind was preferable.


And yes, I do plan on getting in contact with shuttleworth at some point… Likely after Ive got the basic aircraft finished off. Old Warden is about a 2 hour drive away, so not un-doable as a day out either! I already have a few items that I know I would need to ask so eone there/take a specific image to answer a question or two I have about the airframe itself. Would be great to eventually use this sim to help support their work there too if possible!
In terms of my flight model, landing and takeoff is the only bit I’m not very happy with at the moment… Taking about twice the distance to take off and land at the moment, although it will run into a very nasty spin if you do try and stall her out wrong. A number of cases it’s entirely unrecoverable too which is nice!

Great start so far. Keep up the good work.

Sadly i haven’t had all that much time to work on her this week, mainly due to the heat resulting in my daughter taking a good hour or two extra to get to sleep! I have however managed to work on the canopy today, and got it to a decent stage for the exterior modelling at least!

Ignoring the complete lack of any forward view on the ground, actually while flying she’s not too bad!

I think the fuselage shape as a whole is pretty much sorted now… so this weeks job will likely be sorting out the fairings between the wing and fuselage to give me a chance to work on the flaps.

Thanks again for all the support given so far!


Wow. Yeah. Landing is going to be a nail-biter. Going to have to land in VR so I can look around easily!

I should be able to throw together a quick and dirty set of pilot notes for the first release to give people a better idea of how to fly her and her quirks… The more you read the more awkward she gets! What’s even more fun is that it will take you 5 minutes to get her gear down fully, so you’ve got a very long setup and approach needed… To the point its probably worth doing at least 1 or 2 circuits of the Airfield before landing just to pick out some reference points for the final approach

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Congratulations on starting such a great project on a great aircraft and wishing you best of luck

Looking good. Really impressive for your first 3d modelling project as well. I’ll be keeping an eye on the thread and am quite looking forward to flying it. I did fly the one included in FS9 a fair bit back in the day and enjoyed it a lot. We’ve come a long way since then though.


So apparently 1am on a sunday morning is the time i have free to get round to updates!
This week has been pretty slow progress unfortunately. I did also realise that i’d made an error with the cockpit design with some additional struts for the glass which don’t actually exist (had mistaken some of the welded tube skeleton as window frames). So a bit of time was spent correcting and smoothing that, as well as thinning the frames out to a more reasonable thickness, given they’re not structural.

The main addition this week has been the modelling of the flaps! As of now i have finished their animations as well, although there are some teething bugs getting them to show correctly in-game so sadly all i feel it’s worth showing you this week is a generic front-on view of her. (The nacelles have reverted to an earlier state as a result of having to cut away a small section of them for the flaps as per prototype). This coming week will likely have little to no progress made which is worth showing as i will be shifting on to modelling the tail skid and it’s assembly which i believe will run into the week after too!

After which however, i should hopefully be ready to move into building a rough and ready interior ready to texture everything around late July…hopefully i’ll make it for my deadline!


No in-game images this weekend, however i have managed to model and animate the tail skid! I have kept it to the original 1934 open fairing rather than the later fully enclosed fairing as a) it’s shown on the plans i’m using and b) it’s way easier to model. While testing the skid i adjusted some contact points, although i’m not super happy with the way they sit at the moment still. It did however allow me to spot an issue i had with some god-awful ground handling - turns out the skid was only able to move about 20° before, now it can move 90°!

All the big bits have been finished off for the exterior model for now! Although i do need to a few extras like building some braking equipment onto the tyres (there are next to no images which the brakes are clear on the original images, but i’ll be throwing on some reasonably-sized disk brakes on the inside of each set of wheels. The main thing i’d completely forgotten about was adding an exhaust to the engine! So this evenings work was building the shape and lining up each cylinder, i also had to shift the entire engine forward about 1" as it was contacting the wheel fairings - all sorted now!

The plan for this week is to finish up the exhaust and sort out the nacelles to have all their piping and openings, then next week i’ll throw the last bit of detail into the engine bay (she has no back at the moment) and i think i’ll be ready to move onto the cockpit.

As a side note… for those interested in keeping more up-to-date with progress throughout the week, i tend to post images/ videos every so often when i sort stuff out over on the bushleaguelegends discord… even if you’re not a bush pilot it’s worth joining - brilliant community who are happy to help in pretty much every way! (i may have taken her out for a spin from a very sketchy bush strip earlier… turns out she’s a lot bigger and heavier than an xcub)


Another week and and i believe the exterior model is sorted… for now at least!
Built the engine exhaust earlier in the week, some disk brakes and calipers, and a mooring ring for the tail of the aircraft. I also fiddled about with the nacelles to make the cuts look a bit better and line up more sensibly.

The rest of the work i’ve done is going back and fiddling with the prop physics and flight model… I did have the engine speed and airspeeds dialled in before, however the take-off roll was twice as long as it should have been… So i’ve been trying to figure a way to increase the power of her at lower altitudes. This results in many hours of fiddling with numbers in the hope that it gets me a bit closer, finding a solution you’re happy with, only to check it at altitude and suddenly all your top-end power has gone!

When i sort this out to be a little nicer for the take-off roll i plan to move onto throwing together a rough and ready cockpit just so there’s some instruments to use and switches to flick to check different systems are working as intended.


This is strange, the deHavilland Comet was a very futuristic looking airliner with four jets build into the wings.
Is this propeller plane on the screenshots really also named “deHavilland Comet”?

But it looks good! With a full-glass canopy for perfect visibility.

The jet airliner was the D.H.106, built in 1949.

Yes, they were both called Comet. It wasn’t uncommon back in the golden years. Even now we have the Lightning II in RAF service, but in the 60’s we had the original Lightning. Same with the Typhoon.