Too much weight for the DC-9-30 with JT8D-17 engine

[Klaus Hullermann]

Hi there!

I just noticed yesterday that the basepack of the DC-9-30 with -17 engines has a wrong empty weight (I'm using FS9 btw). After checking the other -30 basepacks, I assume that the one with the -17 engines is the only one with a faulty empty weight. It seems that someone put the empty weight of the -50 series into the basepack of the smaller (and lighter!) -30 with JT8D-17 engines. I only looked at the passenger-variants of the -30, since I don't fly any freighters.

I'm surprised that noone ever noticed that before (the DC-9 is offered by HJG several years now)!

Klaus

[aerofoto - HJG Admin]

The CFG stated data is correct .... "within reason"

"Reason" being defined as follows ....

The JT8D-17 powered DC-9-30 aircraft base pack we offer is a specification intended to more closely represent the "DC-9-34CF".

The DC-9-34CF is both the "highest weight and longest ranging" version of the "DC-9-30" family.

The only detail really lacking is the JT8D-17 DC-9-30 base pack we currently offer features 3-tank and not a 4-tank configuration. I "do" have a 4-tank configuration for it .... and which I could offer .... BUT .... during development I decided what we currently have is sufficient for our purposes. We generally develop more than what we ever actually release .... and then release "selectively".

Just a couple of important considerations in respect of this weight related data ....


1. Avoid confusing MZFW with EW references .... I wonder if you might be (not suggesting you are) doing that.

2. The weights we've applied are correct .... "in accordance with the best references we could access" .... at the time. CAUTION HERE THOUGH .... because it's also been our past experience/frustration to source manufacturer, FAA, airport operations, and airline data that can all, sometimes, be in contradiction .... and we've even seen variation among official data from manufacturers too that differs by a fair margin (sometimes though after an aircraft type has been in service for a considerable period of time the originally mandated weights are revised/adjusted and which may account for this to some extent .... as I think happened, at least twice, in the case of the MD-90's .... and has undoubtedly occurred in the case of other aircraft types too). In situations where we're confronted with contradictory evidence .... we're then forced to "use our technical intelligence" in order formulate "an acceptable average" based within the range of the best data available to us .... and which then becomes the weight/s we apply to our simulations. Some sources quote EW for the DC-9-34CF as being around 61,000 LBS .... others state 64,675 LBS (specifically) .... and some even go a wee bit higher again, so, we went with a "64,675" LBS EW and our currently stated 121,000 LB MGW (MRW could possibly be up to 1,000 LBS above this though) .... and which is considered "more than acceptable".

3. The other DC-9-30's we offer (and this applies to sub versions of other aircraft types we represent too) are based on a more-or-less standard EW of around 56,855 LB (although in reality this data differs between each sub version too) .... with stated MGW's of 98,000 LB, 108,000 LB, 110,000 LB, 114,000 LB, and 121,000 LB in accordance with their differing engine thrust (JT8D-7, JT8D-9, JT8D-11, JT8D-15, and JT8D-17 respectively). This's the way HJG's always done things .... "since 2000" .... and continues to do in order to best represent the aircraft types it offers .... since a one specification fits all methodology is just "absolute rubbish" .... and in addition to this there's no point in our doing things along the very same way as others already have. We do things differently.


I wouldn't recommend resetting the CFG stated EW value for the JT8D-17 powered DC-9-30 .... should you be contemplating doing so. Such could possibly (I don't say it will though) adversely impact the MOI influences applied to the (any) simulation .... each of which start based on EW's and also take aircraft dimensions into account too. If using the DC-9 panels we offer any such CFG weight adjustment/s might additionally adversely impact calibration of the V-REF data calculations generated by the weight computer featured within each panel .... just my recommendation only


This next part of my response "IS NOT" directed Klaus's query .... I'm just commenting generally/routinely ....


What we offer in regard to like of the above technical data .... we like to think (since 2000) better reflects the aircraft types we represent despite the slightly greater complexity this may impose. It's all very clearly, and thoroughly, documented within our forum based service notes for each simulation though .... people just have to "READ" the data we compile .... and apply it accordingly in order to avoid problems. What we do .... and the way we do it .... is justified .... to the extent that both myself, and Mike, over the years have determined it only requires some 500 LBS more thrust (per engine) and some few thousand LBS more weight to result in "noticeable differences" in regard to FS flight performance/s .... BUT .... such differences are only evident to the extent these simulations are also flown "properly" for starters. This's why we offer basic flying guides for most of our simulations .... and which work well if adhered to. If one wants to just "fire up" .... then "push the power up" .... and "go off balls-to-the-wall" .... and without performing any W&B adjustment/s or other planning first .... THEN (maybe sadly) .... one's only going to deny themselves experiencing some of the performance variations compiled into each simulation we offer.

To this extent we know precisely what we're doing .... and why

Mark C
AKL/NZ

[Klaus Hullermann]

Thank you Mark for this interesting reply. Again I learned something new about those great jetliners you guys are offering (both from the Real World ones and their virtual counterparts).

I will re-install the -17 basepack of the DC-9-30 to 'delete' my already manipulated DC-9-34 and then I can enjoy her to the full and as intended.

You guys are fantastic!!

Klaus

[aerofoto - HJG Admin]

Just FYI Klaus ....

Among DC-9-30's .... the JT8D-17 wasn't used on just the -34 and 34CF only.

It was also fitted to some -31's, -32's, and -33's too.

BWIA and AVIACO were the primary operators whom each ordered the 34CF and -34 (respectively) straight from the MDC production line, but, some of their aircraft undoubtedly later flew with other carriers too.

BALAIR also operated at least 1 -34 (HB-IDT) as did OZARK too (N928L) .... both delivered new by MDC (according to my production data).

As mentioned above the D-17 was also fitted to some -31's (some of those in service LINEAS AEREAS VENEZOLANAS) and both -32's and -33'3 too (some of those in service with in service with AEROMEXICO). The extra power would undoubtedly have been an considerable advantage to these 2 carriers .... particularly in regard to their hot and high type operations.

Mark C
AKL/NZ

[Klaus Hullermann]

Thanks Mark for the educational reply. Those replies and the great flightline are the things I love about HJG!

You guys rock!!!

Klaus

[aerofoto - HJG Admin]

Klaus .... I may (possibly) send you some information (files) later .... in regard to "how to" hybrid our current DC-9-30 JT8D-9, JT8D-11, and JT8D-15 base packs .... to represent DC-9-31, -32, and -33 specification, and powered by the D-17, and in such a way as it won't/shouldn't then risk destabilizing the current FDE based MOI influences or adversely impacting the weight computed V-REF data for the panel ASI too.

These would be hybrids of what HJG currently offer

I won't post this information publicly though .... because we don't encourage doing this (and some people will only "STUFF IT UP" .... but .... I know you're "technically competent") given we only support what's currently downloadable.

Lt's just see how I go for time (first) .... and subject to other current impositions and commitments

i'll get back yo you (when I can) .... in due course

Mark C
AKL/NZ

[Klaus Hullermann]

Thank you for this generous offer, but you don't have to create hybrids. I'm quite happy with those 'niners' as they are.

Klaus